Upgrade to ManifoldDiff v0.4

[gdalle]

• Bump ManifoldDiff compat to v0.4.0
• Remove import of AbstractDiffBackend

[kellertuer]

One thing that could be done here as well then, is to remove all the requires and using ..X tricks in the extension, since from 1.10 onwards they are not needed. But sure we can also do that on a next PR.

[gdalle]

Good point, I'll do the Julia 1.10 upgrade first and then rebase this PR on it.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.36%. Comparing base (c0a2344) to head (818411b).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #771   +/-   ##
=======================================
  Coverage   96.36%   96.36%           
=======================================
  Files         124      124           
  Lines       11582    11582           
=======================================
  Hits        11161    11161           
  Misses        421      421           

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[gdalle]

@kellertuer this should be good to go