RFR: 8071693: Introspector ignores default interface methods [v3]

[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 one additional commit since the last revision:

  Put braces around single-line "if" statement clauses.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13544/files
  - new: https://git.openjdk.org/jdk/pull/13544/files/e37a1467..0326aa13

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13544&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13544&range=01-02

  Stats: 4 lines in 1 file changed: 2 ins; 0 del; 2 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