[RELAY][BYOC] Fix the creation of tuple of tuples in PartitionGraph (#5616)

[RELAY][BYOC] Fix the creation of tuple of tuples in PartitionGraph (#5616)

* [RELAY][BYOC] Fix the creation of tuple of tuples in PartitionGraph

If the annotated compiler region contains multiple outputs where
some of the outputs are tuple output, the current PartitionGraph will
create tuple of tuples. This will not be handled by the runtime.
This commit flattens the such tuples and re-create them after the
call site of the partitioned function.

Change-Id: I4e7ccbda73c129a9f4ae8705d5c9f2af6ab99ef6

* [RELAY][BYOC] Fix the creation of tuple of tuples in PartitionGraph

    *code refactor : extracted the passes as a sequential

Change-Id: If4bc00b00a96fa244358d602fc1a361498342f46

* [RELAY][BYOC] Fix the creation of tuple of tuples in PartitionGraph
   *further refactor

Change-Id: I69ddd0e835e88ef97da8a3a3b949be3f7b619c02

* [RELAY][BYOC] Fix the creation of tuple of tuples in PartitionGraph
    *class description comment amended

Change-Id: I55720bf0467c96e979e1ab56c40d9d209e0f9456