Routine Bazel builds print the detected toolchain, remote execution container, and a warning whenever GDB indexing is disabled. Remove these notices from local_config_platform.bzl and separate_debug.bzl to reduce build-log noise, along with the message-only rule and dependency in bazel/BUILD.bazel and mongo_src_rules.bzl.

Validation: bazel run format and all 3 existing platform tests passed. Platform-generation outputs were identical before and after the change across 54 host/environment configurations; edited Starlark/BUILD files parsed successfully and git diff --check passed.