[ty] Offer "Did you mean...?" suggestions for unresolved from imports and unresolved attributes (#18705)

Co-authored-by: Brent Westbrook <brentrwestbrook@gmail.com>

crates/ty_python_semantic/resources/mdtest/import/basic.md

@@ -205,3 +205,39 @@ python-version = "3.13"
 import aifc  # error: [unresolved-import]
 from distutils import sysconfig  # error: [unresolved-import]
 ```
+
+## `from` import that has a typo
+
+We offer a "Did you mean?" subdiagnostic suggestion if there's a name in the module that's
+reasonably similar to the unresolved member.
+
+<!-- snapshot-diagnostics -->
+
+`foo.py`:
+
+```py
+from collections import dequee  # error: [unresolved-import]
+```
+
+However, we suppress the suggestion if the only close matches in the module start with a leading
+underscore:
+
+`bar.py`:
+
+```py
+from baz import foo  # error: [unresolved-import]
+```
+
+`baz.py`:
+
+```py
+_foo = 42
+```
+
+The suggestion is never suppressed if the typo itself starts with a leading underscore, however:
+
+`eggs.py`:
+
+```py
+from baz import _fooo  # error: [unresolved-import]
+```