Right now, this is the limit implicitly imposed for spread/apply calls
as to actually do a spread/apply call through CallVarargs, you need to
pass a FixedArray with the args to be pushed.

Likewise, turbofan can only materialize an arguments object with a
backing store of length FixedArray::kMaxLength.

The practical limit that users will actually hit is the stack - this
change doesn't change that, it just documents what the actual limit is.

This would actually allow an embedder/custom fork to increase stack
size and still be able to make spread/apply calls with a large number
of args.

Change-Id: If5e66a61ed3f9df36031eb098646d48fc2ca2507
Reviewed-on: https://chromium-review.googlesource.com/c/1367451Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58119}