Switch the current bool* parameter to a structure that contains
the boolean fallback flag and is forward compatible, if we decide
to add more options to the fallback call.

Fly-by refactoring: moved V8_ENABLE_FP_PARAMS_IN_C_LINKAGE out of
a public V8 header file.

Bug: chromium:1052746
Change-Id: I844db24cc687c58b3c3bbd84b4d61bb4759bcfc7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2474775
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70642}