Add CONST_ITEM_MUTATION lint

Fixes #74053
Fixes #55721

This PR adds a new lint `CONST_ITEM_MUTATION`.
Given an item `const FOO: SomeType = ..`, this lint fires on:

* Attempting to write directly to a field (`FOO.field = some_val`) or
  array entry (`FOO.array_field[0] = val`)
* Taking a mutable reference to the `const` item (`&mut FOO`), including
  through an autoderef `FOO.some_mut_self_method()`

The lint message explains that since each use of a constant creates a
new temporary, the original `const` item will not be modified.

compiler/rustc_mir/src/util/mod.rs

@@ -7,12 +7,14 @@ pub mod storage;
 
 mod alignment;
 pub mod collect_writes;
+mod find_self_call;
 mod graphviz;
 pub(crate) mod pretty;
 pub(crate) mod spanview;
 
 pub use self::aggregate::expand_aggregate;
 pub use self::alignment::is_disaligned;
+pub use self::find_self_call::find_self_call;
 pub use self::graphviz::write_node_label as write_graphviz_node_label;
 pub use self::graphviz::{graphviz_safe_def_name, write_mir_graphviz};
 pub use self::pretty::{dump_enabled, dump_mir, write_mir_pretty, PassWhere};