[red-knot] Consistent suffixes for function names

[sharkdp]

We previously had a scheme where functions that had a _ty suffix would return a Type<'db>. This has been broken in a few places, for example:

• bindings_ty which returns a Symbol<'db>
• declaration_ty which returns a TypeAndQualifiers<'db>

We should probably clean this up, i.e. either come up with new suffixes, with entirely new function names, or decide that we don't want to do anything about it.

[AlexWaygood]

Could we maybe just remove the suffixes? I'm not sure they add much in a Rust codebase, since all functions have return-type annotations anyway.

I also think it's non-obvious to newcomers to the codebase that ty means "type". It took me a while to get used to it and I still don't really love the use of the abbreviation everywhere. (In some cases it's obviously necessary since type is a reserved keyword.)

[MichaReiser]

I do think the suffixes are useful here or we have to come up with new names entirely. E.g. bindings suggests that it returns an iterator, bindings_ty makes it clear it doesn't.

[sharkdp]

I opened a #15618 as a proposal on how to rename bindings_ty and declarations_ty, the two functions for which the inconsistency is most apparent.

I also think it's non-obvious to newcomers to the codebase that ty means "type". It took me a while to get used to it and I still don't really love the use of the abbreviation everywhere. (In some cases it's obviously necessary since type is a reserved keyword.)

I opened another draft which renames all *_ty functions to *_type, just to see how it looks like: #15617. This builds on top of #15618. I personally don't have a preference in either direction. If we rename those suffixes from _ty to _type, we should consider doing something similar for variables as well?