Use std::mem::transmute() to avoid unnecessary clones

[codecov[bot]]

Codecov Report

Merging #685 (e9660bb) into main (8b0e83a) will decrease coverage by 0.01%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #685      +/-   ##
==========================================
- Coverage   88.86%   88.85%   -0.01%     
==========================================
  Files         109      109              
  Lines       24185    24188       +3     
==========================================
+ Hits        21491    21492       +1     
- Misses       2694     2696       +2     

Files Changed	Coverage Δ
crates/escalier_ast/src/visitor.rs	49.45% <100.00%> (ø)
crates/escalier_hm/src/infer.rs	91.91% <100.00%> (+<0.01%)	:arrow_up:
crates/escalier_hm/src/unify.rs	82.75% <100.00%> (+0.02%)	:arrow_up:
crates/escalier_hm/src/util.rs	77.59% <100.00%> (+0.03%)	:arrow_up:

... and 4 files with indirect coverage changes