[ty] Add hint about resolved Python version when a user attempts to import a member added on a newer version (#21615)

## Summary

Fixes https://github.com/astral-sh/ty/issues/1620. #20909 added hints if
you do something like this and your Python version is set to 3.10 or
lower:

```py
import typing

typing.LiteralString
```

And we also have hints if you try to do something like this and your
Python version is set too low:

```py
from stdlib_module import new_submodule
```

But we don't currently have any subdiagnostic hint if you do something
like _this_ and your Python version is set too low:

```py
from typing import LiteralString
```

This PR adds that hint!

## Test Plan

snapshots

---------

Co-authored-by: Aria Desires <aria.desires@gmail.com>

crates/ty_python_semantic/resources/mdtest/snapshots/attributes.md_-_Attributes_-_Attributes_of_standa…_(49ba2c9016d64653).snap

@@ -32,7 +32,8 @@ error[unresolved-attribute]: Module `datetime` has no member `UTC`
 5 | # error: [unresolved-attribute]
 6 | reveal_type(datetime.fakenotreal)  # revealed: Unknown
   |
-info: Python 3.10 was assumed when accessing `UTC` because it was specified on the command line
+info: The member may be available on other Python versions or platforms
+info: Python 3.10 was assumed when resolving the `UTC` attribute because it was specified on the command line
 info: rule `unresolved-attribute` is enabled by default
 
 ```