Option to use USGS geometry

[pjhartzell]

Related Issue(s): None

Description: Added ability to pull geometry from an existing USGS STAC Item in lieu of the current method that computes the geometry from the ANG.txt metadata file. First looks for the USGS STAC in the same location as the XML MTL metadata file. If not there, checks the USGS STAC API. If not found in either location, defaults back to using the ANG.txt data for computing the geometry.

PR checklist:

• [x] Code is formatted (run scripts/format).
• [x] Code lints properly (run scripts/lint).
• [x] Tests pass (run scripts/test).
• [x] Documentation has been updated to reflect changes, if applicable.
• [x] Changes are added to the CHANGELOG.
• [ ] Examples are added to examples/

[pjhartzell]

Since we're using network resources in unit tests, we should probably use vcrpy to record the responses and allow unit tests to run in non-network environments. HMU if you want pointers on setting up vcrpy.

Sweet, yeah, I like this. Implemented.