Add option to exclude by group or wildcard

`maven.artifact` supports exclusions by pair group + artifact. Sometimes we need to exclude several dependencies from one artifact. Being able to do so by group or wildcard could be useful.

Start by tracing how `maven.artifact` currently represents and applies exclusions. Define the intended matching behavior for group-only and wildcard exclusions, including interactions with existing group-plus-artifact pairs. The work is done when the requested exclusion forms are supported and their behavior is verified by the project’s relevant tests.

Written by the indexing model from the issue text.