RFR: 8330969: scalability issue with loaded JVMTI agent [v3]

[Serguei Spitsyn]

> This is a fix of the following JVMTI scalability issue. A closed benchmark with millions of virtual threads shows 3X-4X overhead when a JVMTI agent has been loaded. For instance, this is observable when an app is executed under control of the Oracle Studio `collect` utility.
> For performance analysis, experiments and numbers, please, see the comment below this description.
> 
> The fix is to replace the global counter `_VTMS_transition_count` with the mark bit `_VTMS_transition_mark` in each `JavaThread`'.
> 
> Testing:
>  - Tested with mach5 tiers 1-6

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

  review: correct comments related to VTMS transition counters

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18937/files
  - new: https://git.openjdk.org/jdk/pull/18937/files/03bcfecb..173840b5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18937&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18937&range=01-02

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/18937.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18937/head:pull/18937

PR: https://git.openjdk.org/jdk/pull/18937