chore(ci): remove clippy.sh

- Only one source of truth for lints, main Cargo.toml, making clippy.sh
  unnecessary.
- Warnings no longer denied, only in the CI. To preserve existing
  behaviors users can add `-Dwarnings` to local RUSTFLAGS.

We still need to enforce in workspace tests that all crates inherit
workspace lints.

.github/workflows/main.yml

@@ -18,6 +18,7 @@ on:
 
 env:
   CI: 1
+  RUSTFLAGS: "-D warnings"
 
 # On PR events, cancel existing CI runs on this same PR for this workflow.
 concurrency:

Cargo.toml

@@ -250,14 +250,17 @@ validator = "0.12"
 void = "1.0.2"
 zstd = "0.13.1"
 
+# Note: both rust and clippy lints are warning by default and denied on the CI (see run_tests.py).
+# To deny warnings in local dev env:
+# - In the terminal: add to .bashrc `export RUSTFLAGS="$RUSTFLAGS -Dwarnings"
+# - In vscode, add to settings.json "rust-analyzer.cargo.extraEnv": { "RUSTFLAGS": "-Dwarnings" }
 [workspace.lints.rust]
-future-incompatible = "deny"
-nonstandard-style = "deny"
-rust-2018-idioms = "deny"
+future-incompatible = "warn"
+nonstandard-style = "warn"
+rust-2018-idioms = "warn"
 # See [here](https://github.com/taiki-e/cargo-llvm-cov/issues/370) for a discussion on why this is
 # needed (from rust 1.80).
 unexpected_cfgs = { level = "warn", check-cfg = ['cfg(coverage_nightly)'] }
-warnings = "deny"
 
 [workspace.lints.clippy]
-as_conversions = "deny"
+as_conversions = "warn"