[flake8-simplify] Fix false negatives for shadowed bindings (SIM910, SIM911) (#18794)

<!--
Thank you for contributing to Ruff/ty! To help us out with reviewing,
please consider the following:

- Does this pull request include a summary of the change? (See below.)
- Does this pull request include a descriptive title? (Please prefix
with `[ty]` for ty pull
  requests.)
- Does this pull request include references to any relevant issues?
-->

## Summary
I also noticed that the tests for SIM911 were note being run, so I fixed
that.

Fixes #18777
<!-- What's the purpose of the change? What does it do, and why? -->

## Test Plan
Add regression test
<!-- How was it tested? -->

crates/ruff_linter/resources/test/fixtures/flake8_simplify/SIM910.py

@@ -49,3 +49,9 @@ def foo(some_other: object):
 # OK
 def foo(some_other):
     a = some_other.get('a', None)
+
+
+# https://github.com/astral-sh/ruff/issues/18777
+def foo():
+    dict = {"Tom": 23, "Maria": 23, "Dog": 11}
+    age = dict.get("Cat", None)

crates/ruff_linter/resources/test/fixtures/flake8_simplify/SIM911.py

@@ -23,3 +23,9 @@ for k, v in zip(d2.keys(), d2.values()):  # SIM911
 items = zip(x.keys(), x.values())  # OK
 
 items.bar = zip(x.keys(), x.values())  # OK
+
+# https://github.com/astral-sh/ruff/issues/18777
+def foo():
+    dict = {}
+    for country, stars in zip(dict.keys(), dict.values()):
+        ...