Auto merge of #4650 - main--:patch-1, r=matklad

Document that cargo test --release uses profile.bench

It certainly makes sense but it's still surprising behavior when the docs clearly state `cargo bench` = `profile.bench`, `cargo test` = `profile.test`. Had to dive into the code to figure this out.

src/doc/manifest.md

@@ -309,7 +309,7 @@ debug-assertions = true
 codegen-units = 1
 panic = 'unwind'
 
-# The benchmarking profile, used for `cargo bench`.
+# The benchmarking profile, used for `cargo bench` and `cargo test --release`.
 [profile.bench]
 opt-level = 3
 debug = false