RFR: 8308094: Add a compilation timeout flag to catch long running compilations [v6]

[Manuel Hässig]

> This PR adds `-XX:CompileTaskTimeout` on Linux to limit the amount of time a compilation task can run. The goal of this is initially to be able to find and investigate long-running compilations.
> 
> The timeout is implemented using a POSIX timer that sends a `SIGALRM` to the compiler thread the compile task is running on. Each compiler thread registers a signal handler that triggers an assert upon receiving `SIGALRM`. This is currently only implemented for Linux, because it relies on `SIGEV_THREAD_ID` to get the signal delivered to the same thread that timed out.
> 
> Since `SIGALRM` is now used, the test `runtime/signal/TestSigalrm.java` now requires `vm.flagless` so it will not interfere with the compiler thread signal handlers.
> 
> Testing:
>  - [x] Github Actions
>  - [x] tier1, tier2 on all platforms
>  - [x] tier3, tier4 and Oracle internal testing on Linux fastdebug
>  - [x] tier1 through tier4 with `-XX:CompileTaskTimeout=60000` (one minute timeout) to see what fails (`compiler/codegen/TestAntiDependenciesHighMemUsage2.java`, `compiler/loopopts/TestMaxLoopOptsCountReached.java`, and `compiler/c2/TestScalarReplacementMaxLiveNodes.java` fail)

Manuel Hässig has updated the pull request incrementally with one additional commit since the last revision:

  Apply suggestions from Christian
  
  Co-authored-by: Christian Hagedorn <christian.hagedorn at oracle.com>

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/26023/files
  - new: https://git.openjdk.org/jdk/pull/26023/files/8bb5eb7a..3689fc71

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26023&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26023&range=04-05

  Stats: 3 lines in 2 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/26023.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26023/head:pull/26023

PR: https://git.openjdk.org/jdk/pull/26023