Out-of-place copytri in dense trig functions

[jishnub]

With this, the trig functions work for SMatrixes that don't support setindex!.

julia> S = SMatrix{4,4}(Symmetric(rand(4,4)))
4×4 SMatrix{4, 4, Float64, 16} with indices SOneTo(4)×SOneTo(4):
 0.470973   0.212605   0.0227701  0.744485
 0.212605   0.9227     0.022621   0.0139553
 0.0227701  0.022621   0.0568546  0.767089
 0.744485   0.0139553  0.767089   0.186663

julia> sin(S)
4×4 SMatrix{4, 4, Float64, 16} with indices SOneTo(4)×SOneTo(4):
  0.343589   0.140232    -0.044186     0.566605
  0.140232   0.781448    -0.00290253  -0.0305854
 -0.044186  -0.00290253   0.027389     0.623148
  0.566605  -0.0305854    0.623148     0.0739855

There are some type-inference issues at present, as applydiagonal returns a mutable array, but these may be addressed separately.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.94%. Comparing base (579b5f7) to head (629ce26).
Report is 8 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1224      +/-   ##
==========================================
+ Coverage   91.93%   91.94%   +0.01%     
==========================================
  Files          34       34              
  Lines       15384    15415      +31     
==========================================
+ Hits        14143    14174      +31     
  Misses       1241     1241              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.