RFR: 8374518: C1: Remove dead LinearScanStatistic::Counter::counter_fpu_stack

[Christian Hagedorn]

The usages of `LinearScanStatistic::Counter::counter_fpu_stack` were removed with [JDK-8351156](https://bugs.openjdk.org/browse/JDK-8351156) when the FPU stack support was removed. But the definition in the `Counter` enum was missed to clean up. When now printing the counters with `-XX:+CountLinearScan -XX:+CITime`, we reach a `ShouldNotReach` in `LinearScanStatistic::counter_name()` for `Counter::counter_fpu_stack` because there is no longer an entry there - it's dead.

I added a simple hello world sanity test that runs with `-XX:+CountLinearScan -XX:+CITime`.

Thanks,
Christian

-------------

Commit messages:
 - 8374518: C1: Remove dead LinearScanStatistic::Counter::counter_fpu_stack

Changes: https://git.openjdk.org/jdk/pull/29037/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29037&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8374518
  Stats: 39 lines in 2 files changed: 37 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/29037.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29037/head:pull/29037

PR: https://git.openjdk.org/jdk/pull/29037