RFR: 8364516: Serial: Move class unloading logic inside SerialFullGC::invoke_at_safepoint [v2]

[Sangheon Kim]

On Fri, 1 Aug 2025 09:49:08 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Encapsulating classunloading logic inside `invoke_at_safepoint` and adding doc explaining why the classunloading logic can't be placed at the end of marking during full-gc, like other STW collectors.
>> 
>> Test: tier1-3
>
> Albert Mingkun Yang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   review

Looks good as is.

There are not aligned lines at 714, 715.

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Marked as reviewed by sangheki (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/26588#pullrequestreview-3079869693