[WIP] Sketching IR and parsing support for affine maps, affine expressions

Run test case:

$ mlir-opt test/IR/parser-affine-map.mlir
test/IR/parser-affine-map.mlir:3:30: error: expect '(' at start of map range
#hello_world2 (i, j) [s0] -> i+s0, j)
                             ^

PiperOrigin-RevId: 202736856
13 files changed
tree: 7f716933f63356fc0bb5d01107854cd396cbcf9e
  1. include/
  2. lib/
  3. test/
  4. tools/
  5. LICENSE.TXT