6679: JMC should support project Loom JFR changes

[aymane-harmaz]

This PR :

• adds the virtual attribute to the Thread structure
• makes hashCode and equals use the javaThreadId instead of osThreadId as virtual threads will be attached to the osThreadId = 0

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Progress

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Issue

• JMC-6679: JMC should support project Loom JFR changes (New Feature - P2)

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[bridgekeeper]

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[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[aymane-harmaz]

/template append

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[mlbridge]

Webrevs

• 00: Full (bb48fe50)

[thegreystone]

IIRC javaThreadId can be null for native threads that JFR records (GC/VM/JIT threads, etc.). With the new implementation all native threads will be equal to every other native thread. Under the old code, osThreadId distinguished those threads.

[thegreystone]

Also, isVirtual should be in the IMCMethod interface.

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