Deprecate silent_solver to silent

[ericphanson]

Since now it is being used for Convex's verbosity also (printing the formulation time). It is also shorter which I like. I also set it to turn off the warning for non-optimal solutions for consistency and to reduce clutter in test logs.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.11%. Comparing base (d19955e) to head (2c6937e).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #670      +/-   ##
==========================================
+ Coverage   98.09%   98.11%   +0.02%     
==========================================
  Files          89       89              
  Lines        5150     5157       +7     
==========================================
+ Hits         5052     5060       +8     
+ Misses         98       97       -1     

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[ericphanson]

IMO it would be good for this to be part of v0.16.0 to reduce churn. But it isn’t breaking so it could go in after.