Clarify global exclusions with bzlmod

[joca-bt]

There are two fields related to global exclusions in the bzlmod version, viz. exclusions and excluded_artifacts, and it is not clear what is the difference between them. In the non-bzlmod version there's only excluded_artifacts.

When I try to exclude artifacts through the exclusions field nothing seems to be excluded: the artifacts are still present in the json and listed as dependencies (I'm using a lock file - pinning). When using excluded_artifacts it works as expected.

It seems that the implementation function (maven_impl) doesn't refer to the exclusions field at all. Could this be a leftover that needs to be cleaned?

On Bazel 7.4.1 and rules_jvm_external 6.6.