create_snapshot: add option to allow inplace copy ops

Sometimes for debug purposes we need the merge to run for longer
duration. Allow inplace copy ops with the flag which will increase
the total copy ops, effectively increasing the merge time.

Bug: 416317345

Test: th
Test: create_snapshot product.img product.img --inplace_copy_ops
This test shows that inplace ops are converted to copy ops

Change-Id: I67c1cf542f206a2f651885aa69d7770df4fd4fca
Signed-off-by: Sandeep Dhavale <dhavale@google.com>