Using maven as the repo name causes duplicate warnings when using bzlmod

[jschaf]

Downstream bug in rules_jvm_external: bazelbuild/rules_jvm_external#916

What version of protobuf and what language are you using?

v23.1

What did you expect to see

A clean build when using bzlmod.

What did you see instead?

DEBUG: $TMP/external/rules_jvm_external~/private/extensions/maven.bzl:154:14:
The maven repository 'maven' is used in two different bazel modules,
originally in '<my_workspace>' and now in 'protobuf'

Summarizing @shs96c in bazelbuild/rules_jvm_external#916 (comment)

The common maven repo name allows rulesets to contribute to the user's JARs. However, this implies that maven is for the end user, not for transitive dependencies. If a ruleset needs private dependencies, it should use a custom namespace rather than the maven namespace.

• rules_jvm_external uses rules_jvm_external_deps instead of maven.
• rules_kotlin uses kotlin_rules_maven instead of maven.

Proposed fixes

There are a few ways to fix the logline:

1. Patch protobuf in the Bazel Central Registry rewrite maven to protobuf_maven.
2. Modify the protobuf repo to rewrite maven to protobuf_maven.
3. Fetch the JARs manually without using Maven or rules_jvm_external. Trims the dependency graph a fair bit.

I think 2 is the best short-term option. If you're open to it, I can send a PR.