Improvements to Deflation

[dpanici]

• Implement algorithms from Riley 2024
  • Implement deflated line-search Gauss-Newton algorithm like they use
  • Adapt their algorithm for our usual trust-region approach
• add _equilibrium as attribute of DeflationOperator and test using it in proximal-lsq-exact
  • not sure how this will work, but maybe could be interesting to try out