[MLIR][TOSA] First lowerings from Tosa to Linalg

[MLIR][TOSA] First lowerings from Tosa to Linalg

Initial commit to add support for lowering from TOSA to Linalg. The focus is on
the essential infrastructure for these lowerings and integration with existing
passes.

Includes lowerings for a subset of operations including:
  abs, add, sub, pow, and, or, xor, left shift, right shift, tanh

Lit tests are used to validate correctness.

Differential Revision: https://reviews.llvm.org/D94247