[ty] Improve error messages for unresolved attribute diagnostics (#20963)

## Summary

- Type checkers (and type-checker authors) think in terms of types, but
I think most Python users think in terms of values. Rather than saying
that a _type_ `X` "has no attribute `foo`" (which I think sounds strange
to many users), say that "an object of type `X` has no attribute `foo`"
- Special-case certain types so that the diagnostic messages read more
like normal English: rather than saying "Type `<class 'Foo'>` has no
attribute `bar`" or "Object of type `<class 'Foo'>` has no attribute
`bar`", just say "Class `Foo` has no attribute `bar`"

## Test Plan

Mdtests and snapshots updated

crates/ty_python_semantic/resources/mdtest/call/methods.md

@@ -311,7 +311,7 @@ reveal_type(C.f(1))  # revealed: str
 The method `f` can not be accessed from an instance of the class:
 
 ```py
-# error: [unresolved-attribute] "Type `C` has no attribute `f`"
+# error: [unresolved-attribute] "Object of type `C` has no attribute `f`"
 C().f
 ```