gapic-generator-java v0.0.15

[ggj][engx] chore: remove debug printfs (#627)

* fix: fix dep ordering in Bazel dedupe rules

* feat: add a basic trie

* fix: add hashCode() and equals() to Field

* fix: add equals() and hashCode() for MethodArgument

* feat: add a TriFunction

* feat: add DFS traversal to Trie

* feat: add support for nested method sigs (aip.dev/4232)

* chore: remove debug printfs