RFR: 8341168: Cleanup dead code after JDK-8322630

Mon Sep 30 07:44:04 UTC 2024

[JDK-8322630](https://bugs.openjdk.org/browse/JDK-8322630) / #17495 removed the the concept of ICStubs, InlineCache buffers and related safepoints.

There are a handfull of references and auxiliary constructs still in the code, I propose we clean these out.

This removes the unused:
 * Experimental `InlineCacheBufferSize` option
 * `InlineCacheBuffer_lock` mutex
 * `Thread::_missed_ic_stub_refill_verifier` field
 * `VM_ICBufferFull` VM operation

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Commit messages:
 - 8341168: Cleanup dead code after JDK-8322630

Changes: https://git.openjdk.org/jdk/pull/21255/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21255&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341168
  Stats: 39 lines in 10 files changed: 0 ins; 35 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/21255.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21255/head:pull/21255

PR: https://git.openjdk.org/jdk/pull/21255