Dense jacobians

[gdalle]

Replace linear operators with dense jacobians for the direct linear solver

Type unstable due to AbstractDifferentiation.jl, so i commented it out

Also shortened the benchmark

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +2.44% 🎉

Comparison is base (22c092b) 95.88% compared to head (40c05fb) 98.32%.

❗ Current head 40c05fb differs from pull request most recent head 3c77db4. Consider uploading reports for the commit 3c77db4 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #111      +/-   ##
==========================================
+ Coverage   95.88%   98.32%   +2.44%     
==========================================
  Files           9        9              
  Lines         170      179       +9     
==========================================
+ Hits          163      176      +13     
+ Misses          7        3       -4     

Files Changed	Coverage Δ
src/ImplicitDifferentiation.jl	62.50% <ø> (+50.00%)	⬆️
src/linear_solver.jl	100.00% <ø> (ø)
ext/ImplicitDifferentiationChainRulesCoreExt.jl	100.00% <100.00%> (ø)
ext/ImplicitDifferentiationForwardDiffExt.jl	100.00% <100.00%> (ø)
src/operators.jl	100.00% <100.00%> (ø)

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.