This migrates from the deprecated WORKSPACE style to bzlmod.

Summary of changes :

• Use go 1.24.2 instead of 1.18 which is not supported anymore (golang supports only the last 2 major versions for updates)
• Declare using golang.org/x/tools explicitly in tools.go because it is required for the format script
• Dependency on go bazel-gazelle in BUILD.bazel files is now provided by the gazelle module itself instead of the go.mod equivalent com_github_bazelbuild_bazel_gazelle
• Update gazelle from 0.42.0 to 0.43.0
• Cleanup bazel-diff left over
• Use java 21 instead of java 11
• Use precompiled protobuf to save on build time

There are many other go dependencies that could be updated, but they were not directly required for this migration (even the gazelle update is subjective)

I also kept the rules_go dependency repo_name to the old naming to limit the changes and to be closer to the strict minimum for the bzlmod migration.