[llvm] [TableGen, CodeGen, CHERI] Add support for the cPTR wildcard value type. (PR #158426)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> > Test wouldn't hurt
> 
> Do you have a suggestion or a pointer to an existing test I could model on? I have plenty of integration-level tests of this functionality in the CHERI downstreams, but I don't have a unit test for it, and I'm not sure of a good way to write one.

We've been getting better about adding tablegen tests, particularly for globalisel, so [this](https://github.com/llvm/llvm-project/blob/main/llvm/test/TableGen/GlobalISelEmitter/OverloadedPtr.td) looks most directly applicable 

I added a similar test recently [here](https://github.com/llvm/llvm-project/blob/c80d49590871c2060bbea758e09382bc5f9561c6/llvm/test/TableGen/RegClassByHwMode.td#L456)




https://github.com/llvm/llvm-project/pull/158426