fix: Fix auto-deref operations assigning the wrong result type

[jfecher]

Description

Problem*

Resolves #1899

Summary*

When we encounter foo.bar where foo is a reference, we automatically dereference foo, transforming the code into (*foo).bar. When this happens, we previously accidentally set the type of foo to T and *foo to &mut T instead of the reverse. I've switched the two cases.

Documentation

• This PR requires documentation updates when merged.

  • I will submit a noir-lang/docs PR.
  • I will request for and support Dev Rel's help in documenting this PR.

Additional Context

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.