Permissions language reworked

[nijel]

Proposed changes

Rest of changes from #12449 after splitting out #13364 and #13363.

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 83.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 90.95%. Comparing base (c3b1e8d) to head (fbd2efe).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
weblate/auth/permissions.py	83.33%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #13365   +/-   ##
=======================================
  Coverage   90.95%   90.95%           
=======================================
  Files         604      604           
  Lines       62609    62609           
  Branches     6469     6469           
=======================================
+ Hits        56943    56946    +3     
+ Misses       3984     3982    -2     
+ Partials     1682     1681    -1     

Files with missing lines	Coverage Δ
weblate/auth/permissions.py	90.51% <83.33%> (ø)

... and 2 files with indirect coverage changes