[HotColdSplit] Simplify tests by lowering their splitting thresholds

This gets rid of the brittle/mysterious calls to @sink()/@sideeffect()
peppered throughout the test cases. They are no longer needed to force
splitting to occur.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351480 91177308-0d34-0410-b5e6-96231b3b80d8
25 files changed