Support --incompatible_enable_proto_toolchain_resolution

### Is your feature request related to a problem?

The problem is need to compile protoc instead of using prebuilt binary while building java_grpc_library

### Describe the solution you'd like

Support [--incompatible_enable_proto_toolchain_resolution](https://bazel.build/reference/command-line-reference?hl=en#flag--incompatible_enable_proto_toolchain_resolution) bazel flag so users can override protoc compiled from sources with prebuilt binary, as already done in [rules_python](https://github.com/bazelbuild/rules_python/pull/1577) or WIP in [rules_go](https://github.com/bazelbuild/rules_go/pull/3919)

### Describe alternatives you've considered

### Additional context

Examples of declarations toolchains for other languages that already support the feature [here](https://github.com/aspect-build/toolchains_protoc/blob/main/examples/lang_toolchains/BUILD)

No repository files or tests are named. Start by inspecting the toolchain declarations used by java_grpc_library, then compare them with the rules_python implementation and the examples in aspect-build/toolchains_protoc. Done means supporting --incompatible_enable_proto_toolchain_resolution so users can override the protoc compiled from sources with a prebuilt binary.

Scritto dal modello di indicizzazione a partire dal testo della issue.