Export spatial regions to ecsv

[rosteen]

Reading these back in would be another ticket, but this adds parity with spectral regions so that we have a common file format that both can be written out to. This logic could eventually be moved upstream.

[pllim]

But wait... shouldn't such serialization happen upstream in regions? We don't want to create a format that only we know. regions has its own I/O.

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 7 lines in your changes missing coverage. Please review.

Project coverage is 88.68%. Comparing base (37eba85) to head (c3ef255).
Report is 191 commits behind head on main.

Files	Patch %	Lines
jdaviz/configs/default/plugins/export/export.py	80.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2874      +/-   ##
==========================================
- Coverage   88.72%   88.68%   -0.04%     
==========================================
  Files         111      111              
  Lines       17102    17131      +29     
==========================================
+ Hits        15174    15193      +19     
- Misses       1928     1938      +10     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[rosteen]

We decided offline that it would be better to implement this upstream from the start, closing.