Feature/bfgs restart

[sblauth]

Add the possibility to restart BFGS methods with gradient descent.
Closes #92

[codecov-commenter]

Codecov Report

Merging #93 (464a3b0) into main (8d3530a) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #93      +/-   ##
==========================================
+ Coverage   94.65%   94.67%   +0.02%     
==========================================
  Files          65       65              
  Lines        5439     5455      +16     
==========================================
+ Hits         5148     5164      +16     
  Misses        291      291              

Impacted Files	Coverage Δ
cashocs/io/config.py	100.00% <ø> (ø)
...cs/_optimization/optimization_algorithms/l_bfgs.py	99.28% <100.00%> (+0.10%)	⬆️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more