[ggj][engx] fix: speed up precommit checks with --disk_cache (#264)
[ggj][engx] fix: speed up precommit checks with --disk_cache (#264)

* feat: parse batching descriptor fields

* feat: add Field.isMap and map-parsing test

* feat: add initial batching descriptor field to ServiceStubSettings

* feat: support '? extends Foo' wildcard bounded references

* fix: speed up precommit checks with --disk_cache
googleapis/gapic-generator-java,googleapis/gapic-generator-java