Add __traits(canCall) and __traits(resolve)

[Steven Schveighoffer]

On Saturday, 26 July 2025 at 02:27:08 UTC, Steven Schveighoffer 
wrote:

> ## `__traits(resolve, expression)`

I was informed that opend has a feature similar to this proposal:

__traits(resolveFunctionCall, overloadSet, argTypes...)

While similar, it's not exactly what I want. Because it's not as 
natural as "what would you do if I wrote this expression".

For example, this would not work well with UFCS functions. I'm 
unsure if it works with template functions.

-Steve