This improves type safety and is less verbose. Use SimpleTy only where
an integer is needed like switches or emitting a VBR.

---------

Co-authored-by: Sergei Barannikov <barannikov88@gmail.com>

cPTR is a wildcard CHERI capability value type, used analogously to iPTR. This allows TableGen patterns to abstract over CHERI capability widths.

Co-authored-by: Jessica Clarke <jrtc27@jrtc27.com>

- Use `ArrayRef` instead of `SmallVector` reference in a few places.
- Drop redundant `llvm::` in a few places.

After f9250401ef120a4605ad67bb43d3b25500900498, this function is
tail recursive so it was straightforward to convert this to iteratively
walk the linkd list.

ContractNodes recursively walks forward through a linked list. During
this recursion, Matchers are combined into other Matchers.

Previously the formation of MoveSiblingMatcher was after the
recursive call so it occurred as we were unwinding. If a
MoveSiblingMatcher was formed, we would recursively walk forward
to the end of the linked list again which isn't efficient.

To make this more efficient, move the formation of MoveSiblingMatcher
to the forward pass. Add additional rules to unfold MoveSiblingMatcher
if it would be more efficient to use CheckChildType, CheckChildInteger,
CheckChildSame, etc.

As an added benefit, this makes the function tail recursive which
the compiler can better optimize.

It appears that CheckOpcode is already emitted before CheckType so
this hasn't been doing anything on any in tree targets.