Optimize pairwise for Sinus and scalar inputs

[simsurace]

Summary
A call like kernelmatrix(PeriodicKernel(), rand(1000)) produces a number of allocations of the same order as the size of the kernel matrix because Sinus has a vector parameter and the dispatch hits a path which allocates that for each element of the kernel matrix.

Proposed changes
We add two specialized methods that use broadcast.

What alternatives have you considered?
None.

[codecov]

Codecov Report

Attention: 9 lines in your changes are missing coverage. Please review.

Comparison is base (9a2f7bb) 72.78% compared to head (f990586) 66.57%.

Files	Patch %	Lines
src/distances/sinus.jl	0.00%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #538      +/-   ##
==========================================
- Coverage   72.78%   66.57%   -6.22%     
==========================================
  Files          52       52              
  Lines        1374     1382       +8     
==========================================
- Hits         1000      920      -80     
- Misses        374      462      +88     

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