RFR: 8319244: implement JVMTI handshakes support for virtual threads [v6]

[Serguei Spitsyn]

> The handshakes support for virtual threads is needed to simplify the JVMTI implementation for virtual threads. There is a significant duplication in the JVMTI code to differentiate code intended to support platform, virtual threads or both. The handshakes are unified, so it is enough to define just one handshake for both platform and virtual thread.
> At the low level, the JVMTI code supporting platform and virtual threads still can be different.
> This implementation is based on the `JvmtiVTMSTransitionDisabler` class.
> 
> The internal API includes two new classes:
>   - `JvmtiHandshake` and `JvmtiUnifiedHandshakeClosure`
>   
>   The `JvmtiUnifiedHandshakeClosure` defines two different callback functions: `do_thread()` and `do_vthread()`.
> 
> The first JVMTI functions are picked first to be converted to use the `JvmtiHandshake`:
>  - `GetStackTrace`, `GetFrameCount`, `GetFrameLocation`, `NotifyFramePop`
> 
> To get the test results clean, the update also fixes the test issue:
> [8318631](https://bugs.openjdk.org/browse/JDK-8318631): GetStackTraceSuspendedStressTest.java failed with "check_jvmti_status: JVMTI function returned error: JVMTI_ERROR_THREAD_NOT_ALIVE (15)" 
> 
> Testing:
>  - the mach5 tiers 1-6 are all passed

Serguei Spitsyn has updated the pull request incrementally with one additional commit since the last revision:

  addressed review: (1) removed is_vthread_alive checks; (2) reverted one update

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16460/files
  - new: https://git.openjdk.org/jdk/pull/16460/files/13e05ab1..a526bd60

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16460&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16460&range=04-05

  Stats: 17 lines in 1 file changed: 0 ins; 15 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/16460.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16460/head:pull/16460

PR: https://git.openjdk.org/jdk/pull/16460