RFR: 8341966: Broken annotated module may lead to an exception in javac

[Jan Lahoda]

Consider a `module-info.class`, that both:
 - is wrong, so it will produce a bad-classfile error, for example due to an illegal `requires transitive java.base;`
 - and the module is annotated

If the javac proceeds to resolve the annotations (which is not the default, but can be pushed to do it), it will crash with an `AssertionError` while trying to un-proxy the annotations. This is because there's an assert that `requestingOwner.owner.kind == MDL`, but since the module is erroneous, the kind is `ERR`, and the assert fails.

The proposal is to loosen the assert a bit, and require `requestingOwner.owner instanceof ModuleSymbol`. That should still be sufficiently strong, while permitting broken modules to be handled.

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Commit messages:
 - 8341966: Broken annotated module may lead to an exception in javac

Changes: https://git.openjdk.org/jdk/pull/21486/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21486&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341966
  Stats: 97 lines in 2 files changed: 93 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/21486.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21486/head:pull/21486

PR: https://git.openjdk.org/jdk/pull/21486