Make sign faster.

[bernaferrari]

Inspired by https://www.romainguy.dev/posts/2024/micro-optimizations-in-kotlin-1/

We use on vm and wasm.

We shouldn't use in JsInt because:

JsInt and JsDouble is basically the same thing because they are backed by the same representation (JS number type). In JS bitwise operations truncate the number to 32-bits so you can't really use them for this case.

Java and Kotlin 2.0 are doing this. Benchmark on JVM.

[copybara-service]

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[copybara-service]

https://dart-review.googlesource.com/c/sdk/+/346687 has been updated with the latest commits from this pull request.

[copybara-service]

https://dart-review.googlesource.com/c/sdk/+/346687 has been updated with the latest commits from this pull request.

[copybara-service]

https://dart-review.googlesource.com/c/sdk/+/346687 has been updated with the latest commits from this pull request.