Rollup merge of #140234 - nnethercote:separate-Analysis-and-Results, r=davidtwco

Separate dataflow analysis and results

`Analysis` gets put into `Results` with `EntryStates`, by `iterate_to_fixpoint`. This has two problems:
- `Results` is passed various places where only `Analysis` is needed.
- `EntryStates` is passed around mutably everywhere even though it is immutable.

This commit mostly separates `Analysis` from `Results` and fixes these two problems.

r? `@davidtwco`

compiler/rustc_mir_dataflow/src/lib.rs

@@ -18,8 +18,8 @@ pub use self::drop_flag_effects::{
     move_path_children_matching, on_all_children_bits, on_lookup_result_bits,
 };
 pub use self::framework::{
-    Analysis, Backward, Direction, EntryStates, Forward, GenKill, JoinSemiLattice, MaybeReachable,
-    Results, ResultsCursor, ResultsVisitor, fmt, graphviz, lattice, visit_results,
+    Analysis, Backward, Direction, Forward, GenKill, JoinSemiLattice, MaybeReachable, Results,
+    ResultsCursor, ResultsVisitor, fmt, graphviz, lattice, visit_reachable_results, visit_results,
 };
 use self::move_paths::MoveData;