[Triton-MLIR][BACKEND] add convert_layout[shared->dot_op] converstion to adapt DotOperand layout (#786)

This PR helps to

1. Adapt the existing DotOp conversion to the design of the new
DotOperand layout,
2. Making the DotOp conversion work with both shared-layout inputs case
and dotoperand-layout inputs case for further upstream switch.

lib/Dialect/TritonGPU/IR/Dialect.cpp

@@ -610,4 +610,4 @@ LogicalResult TritonGPUDialect::verifyOperationAttribute(Operation *op,
                                                          NamedAttribute attr) {
   // TODO: fill this.
   return success();
-}
+}