Filter region catalog by flux per tile when converting from tile catalog

[aakashdp6548]

Previously, when converting a TileCatalog to a RegionCatalog we would just discard it if the conversion would produce a region catalog with multiple sources in one tile. Now, we instead keep the highest flux source and turn off all others in that tile.

The high-level algorithm is as follows:

1. Create a unique integer index for each region
2. Unfold with a 3x3 kernel with padding=1 and stride=2 to get number of sources and integer indices in each 3x3 tile
3. Determine which tiles have more than one source and the integer index of those regions
4. For each problematic tile:
    - Get the flux of all "on" sources
    - Find the integer index of the region with the highest flux
    - Turn off all regions in the tile (for simplicity)
    - Turn the max flux region back on

[codecov]

Codecov Report

Merging #938 (14c5840) into master (88e3943) will not change coverage.
The diff coverage is n/a.

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##           master     #938   +/-   ##
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  Coverage   95.82%   95.82%           
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  Files          26       26           
  Lines        3211     3211           
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  Hits         3077     3077           
  Misses        134      134           

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[jeff-regier]

Great. Thanks Aakash!