Bzlmod is getting mature in Bazel 6, it's time for projects to fully adopt Bzlmod, same apply for Bazel itself.

Identified task list:

• remote apis / google apis visibility issue (Fix visibility issue of googleapis and remoteapis with Bzlmod enabled #19057)
• Fetch org_snakeyaml using rules_jvm_external (Fetching testparameterinjector and snakeyaml using rules_jvm_external #19084)
• Fix tests broken due to repository mapping and io_bazel -> _main
  • rlocation in test-setup.sh doesn't respect repo mappings (b20085a)
  • rlocation in test_base.py doesn't respect repo mappings (b66b8c5)
  • Replace io_bazel with _main when necessary
  • Fix other tests that don't respect repo mappings. (9d30849)
• Make bootstrap build work with Bzlmod enabled
• Set up repository cache for integration tests and make sure most of them work without internet access.