ENH: On demand DistanceBand spatial weights (neighbors)

[martinfleis]

In some cases, libpysal.weights.DistanceBand may become too big for memory, e.g. for large thresholds. momepy.DistanceBand mimics its behaviour in terms of .neighbors[key] pattern used within momepy to compute neighbours only on demand to avoid memory issues. It is significantly slower method, but allows large thresholds which would otherwise not fit in memory.

momepy.DistanceBand can be used within most momepy classes directly as spatial_weights instead of libpysal.weights.

[codecov]

Codecov Report

Merging #165 into master will increase coverage by 0.08%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #165      +/-   ##
==========================================
+ Coverage   93.99%   94.07%   +0.08%     
==========================================
  Files           9       10       +1     
  Lines        2597     2633      +36     
==========================================
+ Hits         2441     2477      +36     
  Misses        156      156              

Impacted Files	Coverage Δ
momepy/utils.py	83.33% <ø> (-0.54%)	⬇️
momepy/weights.py	100.00% <100.00%> (ø)

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