RFR: 8334717: Add JVMCI support for APX EGPRs

[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

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Commit messages:
 - address comments
 - Add JVMCI support for APX EGPRs

Changes: https://git.openjdk.org/jdk/pull/23159/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23159&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8334717
  Stats: 546 lines in 18 files changed: 41 ins; 334 del; 171 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