Refactor and DRY up protocol test generation (#3713)

Protocol test generation code was one of the earlier parts of
smithy-rs's codebase and it has accrued a fair amount of tech debt as we
have evolved the code generation primitives. Its code was also forked
when the server code generator was introduced, introducing a lot of
duplicated code that has deviated over time.

This commit refactors the code to modern standards and aims to reconcile
commonalities in `ProtocolTestGenerator`, so that both client and server
can reap centralized improvements over time.

----

_By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice._

aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/AwsFluentClientDecorator.kt

@@ -13,8 +13,7 @@ import software.amazon.smithy.rust.codegen.client.smithy.generators.client.Fluen
 import software.amazon.smithy.rust.codegen.client.smithy.generators.client.FluentClientDocs
 import software.amazon.smithy.rust.codegen.client.smithy.generators.client.FluentClientGenerator
 import software.amazon.smithy.rust.codegen.client.smithy.generators.client.FluentClientSection
-import software.amazon.smithy.rust.codegen.client.smithy.generators.protocol.DefaultProtocolTestGenerator
-import software.amazon.smithy.rust.codegen.client.smithy.generators.protocol.ProtocolTestGenerator
+import software.amazon.smithy.rust.codegen.client.smithy.generators.protocol.ClientProtocolTestGenerator
 import software.amazon.smithy.rust.codegen.core.rustlang.Attribute
 import software.amazon.smithy.rust.codegen.core.rustlang.Feature
 import software.amazon.smithy.rust.codegen.core.rustlang.RustWriter
@@ -28,6 +27,7 @@ import software.amazon.smithy.rust.codegen.core.smithy.RuntimeType
 import software.amazon.smithy.rust.codegen.core.smithy.RustCrate
 import software.amazon.smithy.rust.codegen.core.smithy.generators.LibRsCustomization
 import software.amazon.smithy.rust.codegen.core.smithy.generators.LibRsSection
+import software.amazon.smithy.rust.codegen.core.smithy.generators.protocol.ProtocolTestGenerator
 import software.amazon.smithy.rust.codegen.core.util.letIf
 import software.amazon.smithy.rust.codegen.core.util.serviceNameOrDefault
 import software.amazon.smithy.rustsdk.customize.s3.S3ExpressFluentClientCustomization
@@ -91,7 +91,7 @@ class AwsFluentClientDecorator : ClientCodegenDecorator {
         codegenContext: ClientCodegenContext,
         baseGenerator: ProtocolTestGenerator,
     ): ProtocolTestGenerator =
-        DefaultProtocolTestGenerator(
+        ClientProtocolTestGenerator(
             codegenContext,
             baseGenerator.protocolSupport,
             baseGenerator.operationShape,

codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/client/smithy/ClientCodegenVisitor.kt

@@ -23,7 +23,7 @@ import software.amazon.smithy.rust.codegen.client.smithy.generators.OperationGen
 import software.amazon.smithy.rust.codegen.client.smithy.generators.ServiceGenerator
 import software.amazon.smithy.rust.codegen.client.smithy.generators.error.ErrorGenerator
 import software.amazon.smithy.rust.codegen.client.smithy.generators.error.OperationErrorGenerator
-import software.amazon.smithy.rust.codegen.client.smithy.generators.protocol.DefaultProtocolTestGenerator
+import software.amazon.smithy.rust.codegen.client.smithy.generators.protocol.ClientProtocolTestGenerator
 import software.amazon.smithy.rust.codegen.client.smithy.protocols.ClientProtocolLoader
 import software.amazon.smithy.rust.codegen.client.smithy.transformers.AddErrorMessage
 import software.amazon.smithy.rust.codegen.client.smithy.transformers.RemoveEventStreamOperations
@@ -322,7 +322,7 @@ class ClientCodegenVisitor(
             // render protocol tests into `operation.rs` (note operationWriter vs. inputWriter)
             codegenDecorator.protocolTestGenerator(
                 codegenContext,
-                DefaultProtocolTestGenerator(
+                ClientProtocolTestGenerator(
                     codegenContext,
                     protocolGeneratorFactory.support(),
                     operationShape,

codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/client/smithy/customize/ClientCodegenDecorator.kt

@@ -16,10 +16,10 @@ import software.amazon.smithy.rust.codegen.client.smithy.generators.OperationGen
 import software.amazon.smithy.rust.codegen.client.smithy.generators.ServiceRuntimePluginCustomization
 import software.amazon.smithy.rust.codegen.client.smithy.generators.config.ConfigCustomization
 import software.amazon.smithy.rust.codegen.client.smithy.generators.error.ErrorCustomization
-import software.amazon.smithy.rust.codegen.client.smithy.generators.protocol.ProtocolTestGenerator
 import software.amazon.smithy.rust.codegen.core.rustlang.Writable
 import software.amazon.smithy.rust.codegen.core.smithy.customize.CombinedCoreCodegenDecorator
 import software.amazon.smithy.rust.codegen.core.smithy.customize.CoreCodegenDecorator
+import software.amazon.smithy.rust.codegen.core.smithy.generators.protocol.ProtocolTestGenerator
 import software.amazon.smithy.rust.codegen.core.smithy.protocols.ProtocolMap
 import java.util.ServiceLoader
 import java.util.logging.Logger

codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/client/smithy/customize/ConditionalDecorator.kt

@@ -17,14 +17,14 @@ import software.amazon.smithy.rust.codegen.client.smithy.generators.OperationCus
 import software.amazon.smithy.rust.codegen.client.smithy.generators.ServiceRuntimePluginCustomization
 import software.amazon.smithy.rust.codegen.client.smithy.generators.config.ConfigCustomization
 import software.amazon.smithy.rust.codegen.client.smithy.generators.error.ErrorCustomization
-import software.amazon.smithy.rust.codegen.client.smithy.generators.protocol.ProtocolTestGenerator
 import software.amazon.smithy.rust.codegen.core.smithy.RustCrate
 import software.amazon.smithy.rust.codegen.core.smithy.customize.AdHocCustomization
 import software.amazon.smithy.rust.codegen.core.smithy.generators.BuilderCustomization
 import software.amazon.smithy.rust.codegen.core.smithy.generators.LibRsCustomization
 import software.amazon.smithy.rust.codegen.core.smithy.generators.ManifestCustomizations
 import software.amazon.smithy.rust.codegen.core.smithy.generators.StructureCustomization
 import software.amazon.smithy.rust.codegen.core.smithy.generators.error.ErrorImplCustomization
+import software.amazon.smithy.rust.codegen.core.smithy.generators.protocol.ProtocolTestGenerator
 
 /**
  * Delegating decorator that only applies when a condition is true