TableGen: Introduce `!range` operator for half-opened interval

`!range(a, b)` generates a list `[a,b)`. `a` is optional and `0` by default.

  - `!range(-1, 4)` generates `[-1, 0, 1, 2, 3]`
  - `!range(4)` generates `[0, 1, 2, 3]`
  - `!range(2, 2)` generates `[]<list<int>>`

`!range(list)` is equivalent to `!range(0, !size(list))`.

Differential Revision: https://reviews.llvm.org/D145871