fast path for dists in the PointMass constraint

[bvdmitri]

Previously the PointMass form constraint called slow optimization routine for <: Distribution objects, even though it is easier and faster to return the mode of the distribution. This PR fixes that. Found by @bartvanerp

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.09% 🎉

Comparison is base (6ad864e) 81.22% compared to head (287aa85) 81.32%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #145      +/-   ##
==========================================
+ Coverage   81.22%   81.32%   +0.09%     
==========================================
  Files          11       11              
  Lines        1209     1210       +1     
==========================================
+ Hits          982      984       +2     
+ Misses        227      226       -1     

Files Changed	Coverage Δ
src/constraints/form/form_point_mass.jl	78.37% <100.00%> (+3.37%)	⬆️

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[bartvanerp]

Before:

BenchmarkTools.Trial: 6 samples with 1 evaluation.
 Range (min … max):  929.941 ms …   1.077 s  ┊ GC (min … max):  9.92% … 11.26%
 Time  (median):     957.682 ms              ┊ GC (median):    11.08%
 Time  (mean ± σ):   987.136 ms ± 64.681 ms  ┊ GC (mean ± σ):  11.12% ±  0.82%

  █  █      █ █                                        █     █  
  █▁▁█▁▁▁▁▁▁█▁█▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁█▁▁▁▁▁█ ▁
  930 ms          Histogram: frequency by time          1.08 s <

 Memory estimate: 528.79 MiB, allocs estimate: 4246814.

After

BenchmarkTools.Trial: 7 samples with 1 evaluation.
 Range (min … max):  668.098 ms … 845.756 ms  ┊ GC (min … max):  9.63% … 12.63%
 Time  (median):     725.226 ms               ┊ GC (median):    11.92%
 Time  (mean ± σ):   739.858 ms ±  55.859 ms  ┊ GC (mean ± σ):  11.65% ±  1.28%

  █             █   ██  █            █                        █  
  █▁▁▁▁▁▁▁▁▁▁▁▁▁█▁▁▁██▁▁█▁▁▁▁▁▁▁▁▁▁▁▁█▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁█ ▁
  668 ms           Histogram: frequency by time          846 ms <

 Memory estimate: 485.53 MiB, allocs estimate: 3522721.

[bartvanerp]

Great oneliner! :)