RFR: 7903198: Refine filtering for enums

[Athijegannathan Sundararajan]

backporting the same fix from jdk19

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Commit messages:
 - 7903198: Refine filtering for enums

Changes: https://git.openjdk.java.net/jextract/pull/41/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jextract&pr=41&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7903198
  Stats: 47 lines in 6 files changed: 24 ins; 5 del; 18 mod
  Patch: https://git.openjdk.java.net/jextract/pull/41.diff
  Fetch: git fetch https://git.openjdk.java.net/jextract pull/41/head:pull/41

PR: https://git.openjdk.java.net/jextract/pull/41