RFR: 8351194: Clean up Hotspot SA after 32-bit x86 removal

[Kerem Kat]

Remove 32-bit x86 specific code from the HotSpot Serviceability Agent following the removal of 32-bit x86 support.

- Removed x86-specific implementations and ifdef blocks.
- Renamed files with X86 in the name when they are also used from AMD64, e.g. `X86Frame` → `AMD64Frame`.
- Cleaned up platform detection logic in `PlatformInfo`.
- Updated documentation references.

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Commit messages:
 - Clean up Hotspot SA after 32-bit x86 removal

Changes: https://git.openjdk.org/jdk/pull/27844/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27844&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8351194
  Stats: 2747 lines in 45 files changed: 607 ins; 2094 del; 46 mod
  Patch: https://git.openjdk.org/jdk/pull/27844.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27844/head:pull/27844

PR: https://git.openjdk.org/jdk/pull/27844