Support new naming convention for go_library targets

[tanyabouman]

Have you read the Contributing Guidelines?

Yes

Brief description of what is fixed or changed

By default, Gazelle now uses the last component of the Bazel package, rather than go_default_library as the go_library name.

This causes problems when the naming conventions do not match.
bazel-contrib/bazel-gazelle#980
bazel-contrib/bazel-gazelle#890

Adding support for the new naming convention should not break anything that depends on using the old naming convention, because the Gazelle option import_alias makes aliases to the libraries and this allows the old naming convention to still work.

[achew22]

Good fixup! Thanks for the change