RFR: JDK-8288227: Refactor annotation implementation to use pattern matching for instanceof

[Joe Darcy]

There are many instanceof checks in the sun.reflection.annotation code; these would be improved by using pattern matching for instanceof.

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Commit messages:
 - JDK-8288227: Refactor annotation implementation to use pattern matching for instanceo

Changes: https://git.openjdk.org/jdk/pull/9129/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=9129&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8288227
  Stats: 57 lines in 4 files changed: 1 ins; 14 del; 42 mod
  Patch: https://git.openjdk.org/jdk/pull/9129.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9129/head:pull/9129

PR: https://git.openjdk.org/jdk/pull/9129