Update the bazel docs for bzlmod and gazelle integration

[udf2457]

The doc page for bazel is nice, but it needs updating from two perspectives:

1. WORKSPACE is now considered legacy, and bazel is now recommending bzlmod, i.e. MODULE.bazel. The docs should really be updated to reflect this.
2. Most real-world projects use gazelle to automatically find files and create local BUILD files.

I have been bashing my head against a wall trying to get bazel to work in conjunction with bzlmod and gazelle to compile some gRPC stubs into Go from some proto files. I have been unable to find an end-to-end example that uses both, most examples use WORKSPACE and the few that use bzlmod don't show how to integrate with gazelle !

[drfloob]

That is quite an old blog post, not official documentation per se. Further, gRPC core does not support bazel modules yet. This seems like the sort of thing we could publish a new blog post for eventually, but I'm not sure the libraries are ready for it (I don't think any project other than gRPC-core/C++ uses bazel at all). @udf2457 if you're interested in doing the research, we could consider publishing a new article.