[LinalgExt] Added DecomposeAggregatedOp Pass

[hhkit]

Implementing this pass came up as a result of discussions in #22561, while we were implementing ExpReduction's implementation of AggregatedOpInterface. AggregatedOpInterface exposes decomposeOp which is called as part of a Transform dialect transformation (transform.structured.decompose, transform.iree.decompose_aggregate_op). However, we also call AggregatedOpInterface::decomposeOp as a step in many pipelines.

Therefore, in this PR we:

• Add DecomposeAggregatedOpPass, which calls AggregatedOpInterface::decomposeOp and replaces original uses with the decomposed ops.
• Added tests based on tests in the Transform dialect equivalent

For discussion:

• Should we replace DecomposeAttention with this implementation? I noticed not every AggregatedOp fits into this neatly, as some decompositions (eg. decompose im2col) have custom options to take into account.
• I have asked in Discord and grepped the upstream MLIR code base, because it can't be that something so common doesn't have an upstream equivalent (eg. a pass that invokes a Transform operation?) Happy to close this if anyone knows if there's one!