[mlir] Enable cleanup of single iteration reduction loops being sibling-fused maximally

Changes include the following:
    1. Single iteration reduction loops being sibling fused at innermost insertion level
     are skipped from being considered as sequential loops.
    Otherwise, the slice bounds of these loops is reset.

    2. Promote loops that are skipped in previous step into outer loops.

    3. Two utility function - buildSliceTripCountMap, getSliceIterationCount - are moved from
mlir/lib/Transforms/Utils/LoopFusionUtils.cpp to mlir/lib/Analysis/Utils.cpp

Reviewed By: bondhugula, vinayaka-polymage

Differential Revision: https://reviews.llvm.org/D104249