RFR: 8334717: Add JVMCI support for APX EGPRs

[Doug Simon]

On Thu, 16 Jan 2025 16:01:32 GMT, Yudi Zheng <yzheng at openjdk.org> wrote:

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

LGTM

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Marked as reviewed by dnsimon (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/23159#pullrequestreview-2851438732