cargo: Change prerelease versions to end in ".1-pre" instead of ".0"

So, the prerelease version is "0.9.1-pre" instead of "0.9.0".

The main goal is to make it easier to tell from "jj version" output whether it
describes a released version or a prerelease.

According to https://semver.org/#spec-item-9, if taken as a semver, this would
be ordered after "v0.9.0" and before "v0.9.1" (if we need to have a patch
release). If "v0.9.1" was released, we could move on to "v0.9.2-pre".

Cargo docs imply that they follow this spec closely:
https://doc.rust-lang.org/cargo/reference/resolver.html#semver-compatibility

### Weirder consequences

"v0.9.1-pre.1" would follow "v0.9.1-pre" if we wanted to publish two
such versions to crate.io for some reason (I don't suggest we do this).

In theory, these are sorted alphabetically, so `v0.9.1-beta < v0.9.1-pre <
v0.9.1-rc1`. This is confusing, so we should never have `.1-alpha` or `.1-beta`
(nor probably `.1-rc1`) versions. I propose that if we ever have alpha or beta
versions, they should always be `.0` versions.

Cargo.toml

@@ -5,7 +5,7 @@ resolver = "2"
 members = ["cli", "lib", "lib/testutils", "lib/gen-protos"]
 
 [workspace.package]
-version = "0.9.0"
+version = "0.9.1-pre"
 license = "Apache-2.0"
 rust-version = "1.71"                                 # NOTE: remember to update CI, contributing.md, changelog.md, and flake.nix
 edition = "2021"
@@ -94,7 +94,7 @@ zstd = "0.12.4"
 # put all inter-workspace libraries, i.e. those that use 'path = ...' here in
 # their own (alphabetically sorted) block
 
-jj-lib = { path = "lib", version = "0.9.0" }
+jj-lib = { path = "lib", version = "0.9.1-pre" }
 testutils = { path = "lib/testutils" }
 
 [profile.release]

cli/tests/test_global_opts.rs

@@ -66,7 +66,8 @@ fn test_no_subcommand() {
     insta::assert_snapshot!(stdout.lines().next().unwrap(), @"Jujutsu (An experimental VCS)");
 
     let stdout = test_env.jj_cmd_success(test_env.env_root(), &["--version"]);
-    let sanitized = stdout.replace(|c: char| c.is_ascii_hexdigit(), "?");
+    let sanitized = stdout.replace("-pre", "");
+    let sanitized = sanitized.replace(|c: char| c.is_ascii_hexdigit(), "?");
     assert!(
         sanitized == "jj ?.?.?\n"
             || sanitized == "jj ?.?.?-????????????????????????????????????????\n",