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

[macarte]

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

supports arm64 and x64

note: the AOTEndTrainingOnMethodEntry is ignored when CDSPreImage is specified; this is needed as the phase2 forked java process is passed all phase1 flags along with the -XX:CDSPreImage, but we don't want to run the trigger code in this phase (there may be a better way to handle this state or simply remove the flag from the forked process)

JBS Issue: https://bugs.openjdk.org/browse/JDK-8335358

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Progress

• [x] Change must not contain extraneous whitespace
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Issue

• JDK-8335358: [premain] Explore alternative ways to trigger the end of training run (Enhancement - P3)

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