100% Test coverage all (?) distributions

[JacobHass8]

Added tests for the following distributions to get 100% test coverage.

• arcsine
• bernoulli (97%)
• beta (99%)
  • In find_alpha and find_beta, there isn't an upper bound on the mean and variance. However, there should be.
• binomial (98%)
• cauchy
• chi-squared (98%)

Here is the code coverage report for my information.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.46%. Comparing base (592063d) to head (f2b43c2).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1399      +/-   ##
===========================================
+ Coverage    95.35%   95.46%   +0.10%     
===========================================
  Files          825      825              
  Lines        68310    68412     +102     
===========================================
+ Hits         65139    65308     +169     
+ Misses        3171     3104      -67     

Files with missing lines	Coverage Δ
include/boost/math/distributions/binomial.hpp	98.00% <100.00%> (+11.44%)	⬆️
test/test_arcsine.cpp	99.24% <100.00%> (+0.06%)	⬆️
test/test_bernoulli.cpp	100.00% <100.00%> (ø)
test/test_beta_dist.cpp	98.95% <100.00%> (+0.24%)	⬆️
test/test_binomial.cpp	100.00% <100.00%> (ø)

... and 4 files with indirect coverage changes

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[JacobHass8]

@jzmaddock (or @mborland) you had previously mentioned expanding the existing test coverage. Would this PR be helpful for that? I was just going to keep plugging along for every distribution. Most of the missing tests are for edge cases, or returning NaNs. I've also found a couple of boolean operations that weren't correct which I fixed. There have been a couple cases where something like this appeared (false == check_param1() && check_param2()) when it should have been (false == (check_param1() && check_param2())).