8355227: [lworld] Clarify preview API status for some valhalla APIs

[liach]

Per JEP 12:

In order for frameworks to deliver early support for a preview language feature, frameworks should utilize the reflective preview APIs that are co-developed with it. This will allow frameworks to keep up when programs are written to use the permanent version of the language feature.

According to these rules, the Objects methods and the IdentityException class themselves must be reflective preview APIs: programs compiled without preview feature dependencies that are running with preview features enabled should be able to access these APIs, as at run-time, they may receive value objects and IdentityException thrown by the JVM.

The only remaining essential preview APIs are the constructors of IdentityException: non-preview programs have no reason to construct them.

In addition, fixed a few JEP feature reference: notably, add reference to Strict Fields JEP.

Also, made ClassFile API new models reflective preview APIs - class file processors wish to process structures from preview class files even if the current runtime is not in preview. This is already happening to javac and javap.

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Progress

• Change must not contain extraneous whitespace

Issue

• JDK-8355227: [lworld] Clarify preview API status for some valhalla APIs (Bug - P4)

Reviewing

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8355227: [lworld] Clarify preview API status for some valhalla APIs

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[mlbridge]

Webrevs

• 01: Full (ad5831fc)
• 00: Full (b2727e92)

[liach]

See thread: https://mail.openjdk.org/pipermail/valhalla-dev/2025-April/014045.html

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