8369451: Debug agent support for USE_ITERATE_THROUGH_HEAP is broken and should be removed

[plummercj]

Remove support for the debug agents USE_ITERATE_THROUGH_HEAP support, and the debugflags option used to enable it. Support has been broken for a very long time and can't possibly be relied on by anyone. Please see the CR for a full description.

Note there is a very small compatibility risk with removing the debugflags option (any script that uses it would break). But since it was only used in support of USE_ITERATE_THROUGH_HEAP, is not included in the docs, and is only included in the help output for debug builds, I think the risk is very low. If used, script failures are likely a good thing as it would call attention to the fact that the user is attempting to use functionality that doesn't (and hasn't) worked.

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
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• Commit message must refer to an issue

Issue

• JDK-8369451: Debug agent support for USE_ITERATE_THROUGH_HEAP is broken and should be removed (Bug - P4)

Reviewers

• Serguei Spitsyn (@sspitsyn - Reviewer)
• Alex Menkov (@alexmenkov - Reviewer)

Reviewing

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[openjdk]

@plummercj This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8369451: Debug agent support for USE_ITERATE_THROUGH_HEAP is broken and should be removed Reviewed-by: sspitsyn, amenkov 

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At the time when this comment was updated there had been 24 new commits pushed to the master branch:

• 1992b69: 8369283: Improve trace logs in safepoint machinery
• 501fa20: 8368501: Shenandoah: GC progress evaluation does not use generation
• 37b725d: 8369184: SimpleTimeZone equals() Returns True for Unequal Instances with Different hashCode Values
• ... and 21 more: https://git.openjdk.org/jdk/compare/1aa62dcafd9f11ff3cb191525437e10bb789d276...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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[openjdk]

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[mlbridge]

Webrevs

• 01: Full - Incremental (d6b0e5a2)
• 00: Full (94429a50)

[sspitsyn]

Looks good.