[mlir] Modify LinalgStructuredInterface to allow the computation block to have...

[mlir] Modify LinalgStructuredInterface to allow the computation block to have arguments only for a subset of operands.

Summary:
Currently there is an expectations that there is a corresponsing block argument
for each operand. For some operation, it leads to unused arguments. For example,
in `map`, only input operands are used for the computation.

Differential Revision: https://reviews.llvm.org/D134444