RFR: 7903782: clang warnings and diagnostics below warning level should be logged as well

[Athijegannathan Sundararajan]

Parser logs clang warnings and diagnostics below warning level as well.

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Commit messages:
 - 7903782: clang warnings and diagnostics below warning level should be logged as well

Changes: https://git.openjdk.org/jextract/pull/255/files
  Webrev: https://webrevs.openjdk.org/?repo=jextract&pr=255&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903782
  Stats: 14 lines in 2 files changed: 9 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jextract/pull/255.diff
  Fetch: git fetch https://git.openjdk.org/jextract.git pull/255/head:pull/255

PR: https://git.openjdk.org/jextract/pull/255