RFR: JDK-8309503: Improve javax.lang.model tests for JEP 445

[Joe Darcy]

Improve testing methodology for unnamed classes in javax.lang.model, including coverage of binary names.

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Commit messages:
 - JDK-8309503: Improve javax.lang.model tests for JEP 445

Changes: https://git.openjdk.org/jdk/pull/14321/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14321&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8309503
  Stats: 36 lines in 1 file changed: 17 ins; 11 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/14321.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14321/head:pull/14321

PR: https://git.openjdk.org/jdk/pull/14321