Rollup merge of #107662 - cjgillot:copy-projection, r=oli-obk

Turn projections into copies in CopyProp.

The current implementation can leave behind projections that are moved out several times.

This PR widens the check to turn such moves into copies: a move out of a projection of a copy is equivalent to a copy of the original projection.

diff --cc tests/mir-opt/simple_option_map_e2e.ezmap.PreCodegen.after.mir
index e338f15b4853144be1b1019369f36759a6572516,69d12bc2d5394e28255da860170f5d5e8777a94b..66ba4df767ccf2ff004604ac17d3070affa706c1
--- 1/tests/mir-opt/simple_option_map_e2e.ezmap.PreCodegen.after.mir
--- 2/tests/mir-opt/simple_option_map_e2e.ezmap.PreCodegen.after.mir
+++ b/tests/mir-opt/simple_option_map_e2e.ezmap.PreCodegen.after.mir
@@@ -34,9 -37,15 +34,9 @@@ fn ezmap(_1: Option<i32>) -> Option<i32
      }
  
      bb3: {
-         _4 = move ((_1 as Some).0: i32); // scope 1 at $DIR/simple_option_map_e2e.rs:7:14: 7:15
+         _4 = ((_1 as Some).0: i32);      // scope 1 at $DIR/simple_option_map_e2e.rs:7:14: 7:15
          StorageLive(_5);                 // scope 2 at $DIR/simple_option_map_e2e.rs:7:25: 7:29
 -        StorageLive(_6);                 // scope 2 at $DIR/simple_option_map_e2e.rs:7:25: 7:29
 -        _6 = (move _4,);                 // scope 2 at $DIR/simple_option_map_e2e.rs:7:25: 7:29
 -        StorageLive(_7);                 // scope 2 at $DIR/simple_option_map_e2e.rs:7:25: 7:29
 -        _7 = move (_6.0: i32);           // scope 2 at $DIR/simple_option_map_e2e.rs:7:25: 7:29
 -        _5 = Add(_7, const 1_i32);       // scope 3 at $DIR/simple_option_map_e2e.rs:+1:16: +1:21
 -        StorageDead(_7);                 // scope 2 at $DIR/simple_option_map_e2e.rs:7:25: 7:29
 -        StorageDead(_6);                 // scope 2 at $DIR/simple_option_map_e2e.rs:7:28: 7:29
 +        _5 = Add(_4, const 1_i32);       // scope 3 at $DIR/simple_option_map_e2e.rs:+1:16: +1:21
          _0 = Option::<i32>::Some(move _5); // scope 2 at $DIR/simple_option_map_e2e.rs:7:20: 7:30
          StorageDead(_5);                 // scope 2 at $DIR/simple_option_map_e2e.rs:7:29: 7:30
          goto -> bb4;                     // scope 1 at $DIR/simple_option_map_e2e.rs:10:1: 10:2