Use ruleset specific names for external dependencies

I tried using indexing rules in a large project, but quickly got into conflicting external dependency needs. The most sensitive are grpc/prootbuf related (netty, etc).
Possible solution can be to use ruleset specific external names so that they won't override existing external names. For example, use of `generate_compat_repositories = True,` and default `maven` most likely will overlap with existing externals in a user's project.