RFR: 8340838: Clean up MutableCallSite to use explicit release fence instead of AtomicInteger

[Aleksey Shipilev]

On Tue, 24 Sep 2024 20:21:48 GMT, Chen Liang <liach at openjdk.org> wrote:

> This implementation code was written in JDK 7, before storeFence was available in JDK 8. We should update this legacy code to make it clear.

I have been harboring doubts `syncAll` even works (`FIXME: NYI` is fun) with a lone barrier for about 10-ish years now. But it is irrelevant for the patch at hand, and kicking out excess `AtomicInteger` is good.

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Marked as reviewed by shade (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/21169#pullrequestreview-2328938024