RFR: 8339113: AccessFlags can be u2 in metadata

[Coleen Phillimore]

Please review this change that makes AccessFlags and modifier_flags u2 types and removes the last remnants of Hotspot adding internal access flags.  This change moves AccessFlags and modifier_flags in Klass to alignment gaps saving 16 bytes.  From pahole: so it's a bit better.

before:

        /* size: 216, cachelines: 4, members: 25, static members: 17 */
        /* sum members: 194, holes: 3, sum holes: 18 */


after:

        /* size: 200, cachelines: 4, members: 25, static members: 17 */
        /* sum members: 188, holes: 4, sum holes: 12 */


We may eventually move the modifiers to java.lang.Class but that's WIP.

Tested with tier1-7 on oracle platforms.  Did test builds on other platforms (please try these changes ppc/arm32 and s390).  Also requires minor Graal changes.

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Commit messages:
 - Remove JVM_ACC_WRITTEN_FLAGS because they are all written in the classfile now.
 - 8339113: AccessFlags can be u2 in metadata

Changes: https://git.openjdk.org/jdk/pull/22246/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22246&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339113
  Stats: 167 lines in 41 files changed: 16 ins; 40 del; 111 mod
  Patch: https://git.openjdk.org/jdk/pull/22246.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22246/head:pull/22246

PR: https://git.openjdk.org/jdk/pull/22246