Add BM4D

[smajee]

• Add BM4D with tests and an example (closes issue Add BM4D #183)
• Fix minor bug in BM3D tests

[codecov]

Codecov Report

Merging #263 (e7878b9) into main (31797e2) will decrease coverage by 0.03%.
The diff coverage is 91.30%.

@@            Coverage Diff             @@
##             main     #263      +/-   ##
==========================================
- Coverage   93.75%   93.72%   -0.04%     
==========================================
  Files          50       50              
  Lines        3636     3681      +45     
==========================================
+ Hits         3409     3450      +41     
- Misses        227      231       +4     

Flag	Coverage Δ
unittests	93.72% <91.30%> (-0.04%)	⬇️

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Impacted Files	Coverage Δ
scico/denoiser.py	89.02% <82.60%> (-2.51%)	⬇️
scico/examples.py	95.87% <100.00%> (+0.75%)	⬆️
scico/functional/__init__.py	100.00% <100.00%> (ø)
scico/functional/_denoiser.py	100.00% <100.00%> (ø)

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[bwohlberg]

Note the reasonably significant coverage reduction, which should be addressed.

[bwohlberg]

Docs build issue seems to be resolved by temporary fix. Reduced coverage is the only remaining CI failure.

[bwohlberg]

Looking good: just a few minor issues remaining before it's ready for merging.

[bwohlberg]

I think the trivial -0.04% coverage drop can be ignored. The only remaining unaddressed comment I see is w.r.t. rho tuning in the example script. Probably worth giving that some brief attention if you haven't already, but I'm approving the PR anyway.