Inline the SaveFPMode flag directly into the TSANRelaxedStore stubs:
 - Saves one register for input arguments
 - Avoid branches in the TSANRelaxedStore stubs

Bug: v8:7790, v8:11600
Change-Id: Ib1083f8c1a7e856028ff606ba8c2a93efb10db69
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2917037Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74781}