This switches on a restricted register allocation for all
CSA-generated builtins on ia32, which treats the kRootRegister (=ebx)
as unallocatable.

A few builtins are explicitly excluded. These still need to be fixed
in follow-up CLs. But I'd like to bake this in now to ensure we don't
add more code that cannot handle restricted allocation.

All of this is still behind the (disabled-by-default on ia32)
v8_embedded_builtins configuration.

Bug: v8:6666
Change-Id: If5268aa00439406e1f4e0f7ee18496715a95fdd2
Reviewed-on: https://chromium-review.googlesource.com/1206874Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55654}