add option for tau tolerance in infeasibility check

[chriscoey]

Users rarely need to touch this, but it is useful for MOIPajarito and possibly more generally when "better" infeasibility certificates are desired

[codecov]

Codecov Report

Merging #803 (8682584) into master (4cd922a) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #803      +/-   ##
==========================================
+ Coverage   96.67%   96.71%   +0.03%     
==========================================
  Files          54       54              
  Lines        8371     8374       +3     
==========================================
+ Hits         8093     8099       +6     
+ Misses        278      275       -3     

Impacted Files	Coverage Δ
src/Solvers/Solvers.jl	93.53% <100.00%> (+0.04%)	⬆️
src/Cones/epinorminf.jl	97.83% <0.00%> (-0.37%)	⬇️
src/linearalgebra/dense.jl	68.05% <0.00%> (+5.55%)	⬆️

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