All other simple C functions take a pointer to a stack slot which
contains the actual parameters, whereas the memory_copy_wrapper takes
three parameters. This makes the code generation from Liftoff more
difficult. This CL changes the signature of memory_copy_wrapper to match
the signature of other simple C functions.

As MemoryCopy and MemoryInit are already implemented with C calls, this
change should not make a big difference in terms of performance. Simpler
and smaller Liftoff code may have more effect on performance. If this
assumption turns out wrong, we can change it in the future.

R=clemensb@chromium.org

Bug: v8:10281
Change-Id: I39e0ea00fcb22b4e84e612fe58eb4642856b72c9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2078576
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66607}