RFR: 8356390: Rename ResolvedIndyEntry::set_flags to set_has_appendix

[Johan Sjölen]

The `set_flags` function really only sets whether it has an appendix or not, and there's a separate `set_resolution_failed` method just below that also alters the flag. Just rename this to `set_has_appendix`

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Commit messages:
 - set_flags -> set_has_appendix

Changes: https://git.openjdk.org/jdk/pull/25092/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25092&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8356390
  Stats: 7 lines in 1 file changed: 1 ins; 1 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/25092.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25092/head:pull/25092

PR: https://git.openjdk.org/jdk/pull/25092