Fix bugs related to extent-cropping

[AdeelH]

Overview

Currently in RV, the concept of extent is overloaded to refer to the both the full extent of the data in the data source file as well as a user-specified subset of it. See #1766 for more discussion.

This PR attempts to correct this by disentangling these into extent and bbox. A RasterioSource that reads from a 100x100 GeoTIFF that is cropped to exclude 10 pixels on all sides, for example, will now have .bbox == Box(10, 10, 90, 90) and .extent == Box(0, 0, 80, 80). Moreover, the user is expected to interact with the RasterioSource using local coordinates; i.e. coordinates relative to its bbox rather than global coordinates. See "option 2" here.

Checklist

• Added needs-backport label if PR is bug fix that applies to previous minor release
• Ran scripts/format_code and committed any changes
• Documentation updated if needed
• PR has a name that won't get you publicly shamed for vagueness

Notes

N/A

Testing Instructions

See updated unit tests.

Closes #1766

[codecov]

Codecov Report

Merging #1774 (fd1e94e) into master (cca2580) will increase coverage by 0.02%.
The diff coverage is 85.24%.

❗ Current head fd1e94e differs from pull request most recent head 71b14fe. Consider uploading reports for the commit 71b14fe to get more accurate results

@@            Coverage Diff             @@
##           master    #1774      +/-   ##
==========================================
+ Coverage   79.37%   79.40%   +0.02%     
==========================================
  Files         186      186              
  Lines        8733     8726       -7     
==========================================
- Hits         6932     6929       -3     
+ Misses       1801     1797       -4     

Impacted Files	Coverage Δ
...rvision_core/rastervision/core/data/label/utils.py	100.00% <ø> (ø)
...sion/core/data/label_source/label_source_config.py	100.00% <ø> (ø)
.../rastervision/core/data/label_store/label_store.py	100.00% <ø> (ø)
...vision/core/data/label_store/label_store_config.py	85.71% <ø> (ø)
...e/data/raster_source/multi_raster_source_config.py	68.75% <ø> (ø)
.../core/data/raster_source/rasterio_source_config.py	50.00% <ø> (ø)
...n/pytorch_backend/pytorch_semantic_segmentation.py	57.77% <ø> (ø)
...a/label_store/semantic_segmentation_label_store.py	61.79% <45.45%> (+1.68%)	⬆️
...ource/semantic_segmentation_label_source_config.py	63.15% <50.00%> (ø)
...data/label_store/object_detection_geojson_store.py	68.57% <71.42%> (+1.00%)	⬆️
... and 24 more

... and 2 files with indirect coverage changes