## Summary
No functional change here; this is another simplification split out from
my outcome-refactor branch to reduce the diff there. This merges
`TypeInferenceBuilder::infer_name_load` and
`TypeInferenceBuilder::lookup_name`. This removes the need to have
extensive doc-comments about the purpose of
`TypeInferenceBuilder::lookup_name`, since the method only makes sense
when called from the specific context of
`TypeInferenceBuilder::infer_name_load`.
## Test Plan
`cargo test -p red_knot_python_semantic`