machinery: Add DeepL support for glossaries

[nijel]

Proposed changes

• Add generic mixin to handle service side glossaries
• Implement DeepL integration

Fixes #7086
Fixes #10468
Built on top of #10516

Checklist

• Lint and unit tests pass locally with my changes.
• I have added tests that prove my fix is effective or that my feature works.
• I have added documentation to describe my feature.
• I have squashed my commits into logic units.
• I have described the changes in the commit messages.

Other information

[codecov]

Codecov Report

Attention: Patch coverage is 82.29167% with 17 lines in your changes missing coverage. Please review.

Project coverage is 90.87%. Comparing base (dd88721) to head (96aac97).
Report is 4724 commits behind head on main.

Files with missing lines	Patch %	Lines
weblate/machinery/base.py	73.91%	8 Missing and 4 partials ⚠️
weblate/machinery/deepl.py	84.84%	5 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #10519   +/-   ##
=======================================
  Coverage   90.87%   90.87%           
=======================================
  Files         546      546           
  Lines       56574    56664   +90     
  Branches     9010     9028   +18     
=======================================
+ Hits        51409    51493   +84     
- Misses       3579     3586    +7     
+ Partials     1586     1585    -1     

Files with missing lines	Coverage Δ
weblate/machinery/tests.py	99.84% <100.00%> (+<0.01%)	⬆️
weblate/machinery/deepl.py	91.76% <84.84%> (-4.73%)	⬇️
weblate/machinery/base.py	91.02% <73.91%> (-2.09%)	⬇️

... and 2 files with indirect coverage changes