Part of #4181 and depends on #4183

#4183 introduced the new Fix::safe and Fix::maybe_incorrect constructors. The goal of this task is to go through all usages of Fix::unspecified, Fix::unspecified_edits, Diagnostic::try_set_from_edit, and Diagnostic::set_from_edit and replace them with Fix::safe* or Fix::maybe_incorrect depending on whether the fix is safe or unsafe (may introduce semantic changes).

I recommend creating individual PRs per rule because it makes discussing the safety properties of individual fixes easier.