[Triton] Fixing an issue where LocalAllocOp doesn't support DotOperandEncoding when it calls emitIndices during lowering.
[Triton] Fixing an issue where LocalAllocOp doesn't support DotOperandEncoding when it calls emitIndices during lowering.

The change basically inserts a layout conversion from DotOperandEncoding to the original parent encoding when creating a LocalAllocOp and modifies RemoveLayoutConversions pass to not canonicalize it away.
