RFR: 8335358: [premain] Explore alternative ways to trigger the end of training run [v17]

[Mat Carter]

> AOT training can be ended using either
> 
> - -XX: AOTEndTrainingOnMethodEntry =Hello.someMethod [same syntax as CompileOnly]
> - -XX: AOTEndTrainingOnMethodEntry =Hello.someMethod,Hello.someOtherMethod,count=42
> - jcmd <pid> AOT.end_training
> 
> Also added programmatic hooks to System class:
> - bool System.AOTIsTraining()
> - void System.AOTEndTraining()
> 
> supports arm64 and x64
> 
> note: the AOTEndTrainingOnMethodEntry is ignored when not recording
> 
> JBS Issue: https://bugs.openjdk.org/browse/JDK-8335358

Mat Carter has updated the pull request incrementally with one additional commit since the last revision:

  Added programmatic AOT(Is|End)Training calls to System class

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

Changes:
  - all: https://git.openjdk.org/leyden/pull/21/files
  - new: https://git.openjdk.org/leyden/pull/21/files/88200565..62afc306

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=leyden&pr=21&range=16
 - incr: https://webrevs.openjdk.org/?repo=leyden&pr=21&range=15-16

  Stats: 57 lines in 6 files changed: 56 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/leyden/pull/21.diff
  Fetch: git fetch https://git.openjdk.org/leyden.git pull/21/head:pull/21

PR: https://git.openjdk.org/leyden/pull/21