feat: add fs copy-on-write support

[anonrig]

This slightly improves the performance for certain platforms

[codecov-commenter]

Codecov Report

Merging #40 (3dd1485) into main (72ec745) will decrease coverage by 0.03%.
Report is 1 commits behind head on main.
The diff coverage is 94.44%.

@@            Coverage Diff             @@
##             main      #40      +/-   ##
==========================================
- Coverage   82.22%   82.19%   -0.03%     
==========================================
  Files          21       21              
  Lines        1035     1039       +4     
==========================================
+ Hits          851      854       +3     
- Misses        184      185       +1     

Files Changed	Coverage Δ
crates/tarball/src/lib.rs	97.10% <ø> (ø)
crates/package_manager/src/package_import.rs	84.61% <90.90%> (-1.75%)	⬇️
crates/cafs/src/lib.rs	98.03% <100.00%> (ø)