Don't make copies of input Stores fully overlapping outputs

[manopapad]

Currently, if there is (full or partial) overlap between an input and an output Store in an operation, we handle this at the cuNumeric level, since the core will not do this check for us:

if store1.overlaps(store2):
  store1 = store1.copy()
task.add_input(store1)
task.add_output(store2)

However, if the following are all true:

• store1 and store2 are backed by the same RegionField (as a corollary, they overlap fully)
• store1 and store2 have the same store transformation (may be unnecessary?)
• task.add_alignment(store1, store2)
• an unrelated bug is fixed in the core, see Add missing store overlap checks #1111 (comment)

then we can avoid making the copy, because we can expect the core to coalesce the read requirement for store1 and the write requirement for store2 into the same read-write requirement.

We must be certain that the core will apply the coalescing transformation, otherwise we will get tasks with conflicting region requirements, which Legion will not catch in release mode.