Fix bug in lift_reduce_constant

[SamirDroubi]

• We should verify that the costant being lift is a loop invariant before lifting it.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 86.94%. Comparing base (b2f630f) to head (1806fd1).

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #627 +/- ## ========================================== + Coverage 86.92% 86.94% +0.01% ========================================== Files 94 94 Lines 21837 21851 +14 ========================================== + Hits 18982 18998 +16 + Misses 2855 2853 -2 ```

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