This is the first (and major) step towards converting CallApiCallback
and CallApiGetter stubs into builtins.

The CallApiCallbackStub was parameterized with the number of arguments
passed on the stack. This CL converts the compile-time parameter into
an explicit runtime parameter, and removes all uses of the stub
parameter.

Drive-by: The implementation is now mostly consistent across platforms.
Drive-by: Refactor the calling convention to free up two registers
(kCallData and kHolder are now passed on the stack).

Bug: v8:7777
Change-Id: I212dccc2930de89c264a13755918c9fae7842f1f
Reviewed-on: https://chromium-review.googlesource.com/c/1354887
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58005}