Development of text spotting code

[rwood-97]

Summary

This PR adds some development to the text spotting code:

• Adds dataclasses for text predictions
• Relatively minor refactoring
• Adds saving text predictions as centroid when calling save_to_geojson
• Adding loading/saving of predictions

Fixes #504
Fixes #498
Addresses #533

Checklist before assigning a reviewer (update as needed)

• Self-review code
• Update changelog
• Ensure submission passes current tests
• Add tests
• Update relevant docs

Reviewer checklist

Please add anything you want reviewers to specifically focus/comment on.

• Everything looks ok?

[codecov]

Codecov Report

Attention: Patch coverage is 92.33279% with 47 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
mapreader/spot_text/runner_base.py	79.55%	46 Missing ⚠️
mapreader/spot_text/dptext_detr_runner.py	83.33%	1 Missing ⚠️

Flag	Coverage Δ
unittests	78.98% <92.33%> (+1.15%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
mapreader/spot_text/dataclasses.py	100.00% <100.00%> (ø)
mapreader/spot_text/deepsolo_runner.py	82.14% <100.00%> (ø)
mapreader/spot_text/maptext_runner.py	82.75% <100.00%> (ø)
tests/test_text_spotting/test_deepsolo_runner.py	100.00% <100.00%> (ø)
tests/test_text_spotting/test_dptext_runner.py	100.00% <100.00%> (ø)
tests/test_text_spotting/test_maptext_runner.py	100.00% <100.00%> (ø)
mapreader/spot_text/dptext_detr_runner.py	88.46% <83.33%> (-1.10%)	⬇️
mapreader/spot_text/runner_base.py	79.41% <79.55%> (+9.36%)	⬆️

[kallewesterling]

A few comments, with suggestions of a few things to change here. Nothing major - looks great otherwise!!! :)