Forbidden APIs check fails - missing bundled signatures for java 12

[not-napoleon]

Failure repros locally for me against master with:
./gradlew client:test:forbiddenApisMain -Dcompiler.java=11 -Druntime.java=12

Links to failing builds:
https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+master+matrix-java-periodic/ES_BUILD_JAVA=openjdk12,ES_RUNTIME_JAVA=openjdk12,nodes=virtual&&linux/144/console

https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+master+matrix-java-periodic/ES_BUILD_JAVA=java11,ES_RUNTIME_JAVA=openjdk12,nodes=virtual&&linux/144/console

Prior work:
We encountered this issue before with Java 11, see #33082 . In that case, we were still using a forked version of the ForbiddenApis check, and the fix (found at #33116) looks like it would have also prevented this issue. Some time after that, however, we went back to using the mainline plugin, see PR here #33809 and discussion here #33759

[elasticmachine]

Pinging @elastic/es-core-infra