added: current estimate x̂ and last input lastu in getinfo dictionnary for MPCs

[franckgaga]

Those 2 fields are useful for reproducing specific control periods in which the solver failed, for example.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.59%. Comparing base (4aee803) to head (dd66aed).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #339   +/-   ##
=======================================
  Coverage   98.59%   98.59%           
=======================================
  Files          27       27           
  Lines        5187     5190    +3     
=======================================
+ Hits         5114     5117    +3     
  Misses         73       73           

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