More fork tests, bug fixes in fork passes and GPU backend

• Fix bug in reduce cycles analysis.
• Fix bug in no reset collection constants analysis.
• Modify FloatCollections to allow application on certain functions in module.
• Move fork_split to fork_transforms.rs.
• Refactor fork split and unforkify to have helpers for splitting / unforkifying a single fork-join.
• Add fixup stage to GCM to split and unforkify "problematic" fork-joins.
• Fix anti-dependency calculation when fork-joins are involved.
• Fixed bugs in GPU backend related to ordering of emitting basic blocks.
• Add new fork-join tests (that found all of the above issues).

requested review from @xrouth2

assigned to @rarbore2

added 1 commit

• d21fbc14 - whoops

Compare with previous version

mentioned in commit f847ee50

merged