Revert "[Polly] Implement user-directed loop distribution/fission."

This reverts commit 52c30adc7dfe6334b71adf256d81f70e7b976143 which
breaks the build when NDEBUG is defined.

GitOrigin-RevId: c7bcd72a38bcf99e03e4651ed5204d1a1f2bf695
10 files changed