RFR: 8345678: compute_modifiers should not be in create_mirror

[Coleen Phillimore]

This moves the modifier_flag computation to when InstanceKlass, ObjArrayKlass and TypeArrayKlass are created.

Tested with jck:vm and tier1-4.

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Commit messages:
 - 8345678: compute_modifiers should not be in create_mirror

Changes: https://git.openjdk.org/jdk/pull/22618/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22618&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8345678
  Stats: 39 lines in 8 files changed: 19 ins; 16 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/22618.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22618/head:pull/22618

PR: https://git.openjdk.org/jdk/pull/22618