RFR: 8307399: get rid of compatibility ThreadStart/ThreadEnd events for virtual threads

[Serguei Spitsyn]

The compatible lifecycle `ThreadStart/ThreadEnd` events were added in JDK 19 to support legacy virtual thread unaware JVMTI agents which do not enable the can_support_virtual_threads capability. When this capability is enabled then the `VirtualThreadStart/VirtualThreadEnd` instead of the `ThreadStart/ThreadEnd` events are generated for virtual threads and can be managed (enabled/disabled) separately. If the the `can_support_virtual_threads` capability is disabled then the `ThreadStart/ThreadEnd` events are generated for virtual threads.
This enhancement is to get rid of the compatible lifecycle `ThreadStart/ThreadEnd` events.
Motivation: Performance overhead from compatible lifecycle events can be significant when a lot of virtual threads are created.

Also, there is an experimental VM flag `PostVirtualThreadCompatibleLifecycleEvents` (enabled by default).
If it is turned on then the default compatible lifecycle `ThreadStart/ThreadEnd` events for virtual threads are generated. This VM flag has to be removed now.

Testing:
The mach5 tiers 1-6 were submitted and passed.

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Commit messages:
 - 8307399: get rid of compatibility ThreadStart/ThreadEnd events for virtual threads

Changes: https://git.openjdk.org/jdk/pull/13874/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13874&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307399
  Stats: 70 lines in 6 files changed: 18 ins; 29 del; 23 mod
  Patch: https://git.openjdk.org/jdk/pull/13874.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13874/head:pull/13874

PR: https://git.openjdk.org/jdk/pull/13874