[mlir][scf] Return `replacements` explicitly in `SCFTilingResult`. (#143217)
In #120115 the replacements for the tiled operations were wrapped within
the `MergeResult` object. That is a bit of an obfuscation and not
immediately obvious where to get the replacements post tiling. This
changes the `SCFTilingResult` to have `replacements` explicit (as it was
before that change).
`mergeOps` is added as a separate field of `SCFTilingResult`, which is
empty when the reduction type is `FullReduction`.
This is a API breaking change. All uses of `mergeResult.replacements`
should be replaced with `replacements`.
There was also an implicit assumption that
`PartialReductionTilingInterface` is derived from `TilingInterface`, so
all ops that implemented the `PartialReductionTilingInterface` were
expected to implement the `TilingInterface` as well. This pre-dated the
existence of derived inheritances. Make
`PartialReductionTilingInterface` derive from `TilingInterface`.
Signed-off-by: MaheshRavishankar <mahesh.ravishankar@gmail.com>