RFR: 8071693: Introspector ignores default interface methods [v4]

[Archie L. Cobbs]

> The `Introspector` class was never updated to include `default` methods inherited from interfaces.
> 
> This patch attempts to fix that omission.

Archie L. Cobbs has updated the pull request incrementally with two additional commits since the last revision:

 - Verify static method is not mistakenly identified as property getter.
 - Use Modifier.isAbstract() convenience method instead of bit masking test.

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/13544/files
  - new: https://git.openjdk.org/jdk/pull/13544/files/0326aa13..106edcd6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13544&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13544&range=02-03

  Stats: 5 lines in 2 files changed: 4 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13544.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13544/head:pull/13544

PR: https://git.openjdk.org/jdk/pull/13544