* [RELAY] Fixed issues with MergeCompilerRegions

This PR addresses a few outstanding issues with
the implementation of MergeCompilerRegions. In
particular, it now handles TupleGetItem nodes properly
and other minor bugs related to region merging have
been fixed.

Change-Id: I07783afc56183a6f798a510209f23b0a5f252255

* Fixed issue using pre-merged regions

Change-Id: I0a844ac59bda1089ae0c67cef52f0b0c7ab2cbd7

* Removed some debugging logic

Change-Id: Ib6f2eede6f38bbb270073eb8d4c4dc19f60832c6

* Remove default annotations

Change-Id: I9b7696a51c95871491cbea33c40f92ec327e417f

* Annotate default 'if's

Change-Id: I0098bd1bf6788dd6366810dcefa84f1ebbffaab0

* Clang format

Change-Id: I944365cd3080a97a9261f643a8f1efa5a63cf82b

* Use src/dest in merge

Change-Id: Ie43113492bda8f1ce63eaf9615cb645bb9e2ee86

* Fixed partition test

Change-Id: I46f9e349b1a813a9140f7e4f8a2241687e2df73b

* Removed comments

Change-Id: I309afdd1951d7e796e41d13788aa487707e0ac4c