Especially in wasm, many builtins don't actually need a context
parameter. We currently pass Smi::kZero instead. This CL allows to
generate a CallDescriptor for calling stubs without passing a context,
resulting in reduced compile time and code size, and increased
performance when executing these builtins.

We were calling the ThrowWasm* functions without passing a context
anyway (directly from code-generator-<arch>.h). With this change, we
will also call the StackCheck builtin without passing a (null) context.
This saves two bytes of code in each function plus each loop, and also
slightly reduces compile time (very noisy, but statistically
significant).

Drive-by: Use NoContextConstant instead of SmiConstant(Smi::kZero).

R=mstarzinger@chromium.org, ahaas@chromium.org

Change-Id: If794cc4c262a9cca8d29a68010803c01a2eef4a3
Reviewed-on: https://chromium-review.googlesource.com/541423Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46044}