This removes special-casing of boxes from `rustc_pattern_analysis`, as a
first step in replacing `box_patterns` with `deref_patterns`.
Incidentally, it fixes a bug caused by box patterns being represented as
structs rather than pointers, where `exhaustive_patterns` could generate
spurious `unreachable_patterns` lints on arms required for
exhaustiveness; following the lint's advice would result in an error.
Fix codegen of uninhabited PassMode::Indirect return types.
Add codegen test for uninhabited PassMode::Indirect return types.
Enable optimizations for uninhabited return type codegen test
Unify the output of `suggest_assign_value` and `ty_kind_suggestion`.
Ideally we'd make these a single function, but doing so would likely require modify the crate dependency tree.
mark `min_exhaustive_patterns` as complete
This is step 1 and 2 of my [proposal](https://github.com/rust-lang/rust/issues/119612#issuecomment-1918097361) to move `min_exhaustive_patterns` forward. The vast majority of in-tree use cases of `exhaustive_patterns` are covered by `min_exhaustive_patterns`. There are a few cases that still require `exhaustive_patterns` in tests and they're all behind references.
r? ``@ghost``
