RFR: 8036580: CHA: improve default method support

[Vladimir Ivanov]

Enable CHA to look for unique concrete methods under default interface methods.
Only vtable-based implementation is affected. Old implementation is left as is.

The unit test requires #4211/#4212 to pass and relies on test code refactorings from #4213.

Testing:
- [x] hs-tier1 - hs-tier9

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Depends on: https://git.openjdk.java.net/jdk/pull/4213

Commit messages:
 - Test case
 - Enable default root method support

Changes: https://git.openjdk.java.net/jdk/pull/4214/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4214&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8036580
  Stats: 238 lines in 6 files changed: 216 ins; 9 del; 13 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4214.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4214/head:pull/4214

PR: https://git.openjdk.java.net/jdk/pull/4214