Keep implications between restarts

[Opt-Mucca]

This PR changes the data structure holding implication information to a HighsHashTree (similar to vbs). It now transfers implication information between restarts, shrink-problem calls, and sub-mips. This has been a long-standing TODO in the code, but with low priority because it's not going to be too performance changing.

Pros:

• We now save implications from a cut or conflict that were not copied over between restarts. We also save implications from columns that may not have been re-probed on.
• Implications are now valid throughout the entire presolve code and can be used in more complicated reductions down the line.
• Can now add implications from multiple places without corrupting the data structure

Cons:

• There's some overhead to all the new data structures (probably minor, but still).

Testing locally I'm getting a 0.5% slowdown but solving two more instances. I'd say this is mostly noise and I'd wait for @fwesselm to try it on a larger test set.

[codecov]

Codecov Report

❌ Patch coverage is 99.15254% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 72.78%. Comparing base (2b3c167) to head (3736bd2).
⚠️ Report is 326 commits behind head on latest.

Files with missing lines	Patch %	Lines
highs/mip/HighsImplications.cpp	99.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           latest    #3209      +/-   ##
==========================================
- Coverage   73.18%   72.78%   -0.41%     
==========================================
  Files         432      444      +12     
  Lines      105505   107458    +1953     
  Branches    16991    17294     +303     
==========================================
+ Hits        77217    78212     +995     
- Misses      28012    28969     +957     
- Partials      276      277       +1     

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