RFR: 8321122: Shenandoah: Remove ShenandoahLoopOptsAfterExpansion flag

[Kelvin Nilsen]

On Thu, 30 Nov 2023 16:00:17 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> More flags cleanup. `ShenandoahLoopOptsAfterExpansion` was added long time ago to gate more aggressive barrier optimizations in C2. It was default since then. There seem to be no reason to keep it as the flag. Just checking, @rwestrel -- you don't need it anymore, right?
> 
> Additional testing:
>  - [x] `hotspot_gc_shenandoah`

This looks good to me, though I don't have full understanding of all the relevant issues.

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Marked as reviewed by kdnilsen (no project role).

PR Review: https://git.openjdk.org/jdk/pull/16908#pullrequestreview-1757916271