RFR: 8339113: AccessFlags can be u2 in metadata [v8]

[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.

Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:

  Import @offamitkumar patch for s390.

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/22246/files
  - new: https://git.openjdk.org/jdk/pull/22246/files/5a84b139..8cafd452

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22246&range=07
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22246&range=06-07

  Stats: 32 lines in 5 files changed: 15 ins; 0 del; 17 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