RFR: 8334717: Add JVMCI support for APX EGPRs [v2]

[Yudi Zheng]

> This PR marks extra general purpose registers introduced by Intel APX as Graal allocatables. It also drops AMD64/AArch64/RISCV64.flags and RegisterArray

Yudi Zheng has updated the pull request incrementally with one additional commit since the last revision:

  fix tests

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Changes:
  - all: https://git.openjdk.org/jdk/pull/23159/files
  - new: https://git.openjdk.org/jdk/pull/23159/files/aabb8996..37e4d2a4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23159&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23159&range=00-01

  Stats: 15 lines in 3 files changed: 3 ins; 0 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/23159.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23159/head:pull/23159

PR: https://git.openjdk.org/jdk/pull/23159