RFR: 8345169: Implement JEP 503: Remove the 32-bit x86 Port

[Coleen Phillimore]

On Tue, 4 Mar 2025 16:52:16 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> This PR implements JEP 503: Remove the 32-bit x86 Port.
> 
> The JEP is proposed to target 25, we would not integrate until JEP is ready. Reviews are appreciated meanwhile.
> 
> This is only the removal of obvious 32-bit x86 parts, mostly files with `x86_32` in their name.  Those are only built when build system knows we are compiling for x86_32. There is therefore no impact on x86_64. The approach for removing x86_32 files only also makes this PR borderline trivial, and requires no additional testing beyond normal pre-integration checks.
> 
> The rest of the code is quite heavily intertwined with x86_64 and/or Zero, and would require accurate untangling. It would be much easier to review and test once we purge the free-standing parts of 32-bit x86 port, which is also a bulk of the port. The tangling with 32-bit x86 Zero is also why I did not touch most of the build system paths that handle x86. There is [JDK-8351148](https://bugs.openjdk.org/browse/JDK-8351148) umbrella that tracks further cleanup work. One can peek the final state that can be reached with all the cleanups in my earlier exploratory https://github.com/openjdk/jdk/pull/22567.
> 
> Additional testing:
>  - [x] Linux x86_32 Server fastdebug, `make bootcycle-images` (now fails configure)
>  - [x] Linux x86_64 Server fastdebug, `make bootcycle-images` (still works)
>  - [x] Linux x86_32 Zero fastdebug, `make bootcycle-images` (still works)
>  - [x] Linux x86_64 Zero fastdebug, `make bootcycle-images` (still works)

I agree with @iwanowww's and @shipilev comments.  I would like to see this be the JEP implementation and the additional cleanups, particularly in the interpreter, handled one by one.  I don't see any advantage for one big integration push.  It'll be disruptive and for this, there is no scenario where this would be helpful to any future work.
When Aleksey sent out the original PR there were cleanups that needed explanation.  Finding the explanations in the big PR is a pain for scrolling.  And the reviewers for that part of the change were a different set than ones needed for this change.  Again for no benefit.

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Marked as reviewed by coleenp (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/23906#pullrequestreview-2664309410