[SE-0251] Additions to SIMD types. (swiftlang#23421)

* Additions to SIMD types.

- extension from 2 and 3-element vectors to 3- and 4-element vectors.
- the .one member
- swizzles via subscript-by-simd
- min/max/sum reductions
- min/max/clamp on vectors-of-comparable
- any and all

- Make permute subscript wrap on vector length, even for SIMD3 dictionaries. Also restore min/max to globals, rather than static functions.

Author: stephentyrone