RFR: 8208237: Re-examine defmeth tests and update as needed

[Vladimir Ivanov]

Some test cleanups:
- removed all `@KnownFailure`
- narrowed expected error types in some cases
- fixed private method invocation tests in reflection mode (got rid of `NoSuchMethodError`s in reflection mode)
- introduced `TesterBuilder::new_()` to let the tests precisely describe the intent
- some other minor cleanups

Testing:
- [x] defmeth tests
- [x] hs-tier5 - hs-tier6 (include defmeth tests)

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Commit messages:
 - Misc cleanups
 - PrivateMethodsTest
 - Constructor call support
 - Refactor vm.runtime.defmeth tests

Changes: https://git.openjdk.java.net/jdk/pull/3879/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3879&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8208237
  Stats: 663 lines in 20 files changed: 132 ins; 356 del; 175 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3879.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3879/head:pull/3879

PR: https://git.openjdk.java.net/jdk/pull/3879