RFR: 8317300: javac erroneously allows "final" in front of a record pattern

[Aggelos Biboudis]

Introduces the relevant check for `final` in record patterns.

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Commit messages:
 - 8317300: javac erroneously allows "final" in front of a record pattern

Changes: https://git.openjdk.org/jdk/pull/15997/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15997&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8317300
  Stats: 30 lines in 3 files changed: 30 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/15997.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15997/head:pull/15997

PR: https://git.openjdk.org/jdk/pull/15997