[benchmarks] Add MemoryCopy benchmark suite.

The MemoryCopy benchmark suite measures the overhead of copying
data between compatible TypedData or Pointer values.

Change-Id: Iaf5ea27b7f9177f4800880da36234afd2b908db2
Bug: #42072
Bug: b/294114694
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/318661
Reviewed-by: Martin Kustermann <[email protected]>
Commit-Queue: Tess Strickland <[email protected]>

Author: sstrickl