RFR: 8071693: Introspector ignores default interface methods [v7]

[Archie Cobbs]

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

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

 - Jam lines into 80 columns.
 - Add more scenarios to the regression test.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13544/files
  - new: https://git.openjdk.org/jdk/pull/13544/files/8c129960..e6a2ecba

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13544&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13544&range=05-06

  Stats: 140 lines in 1 file changed: 118 ins; 0 del; 22 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