SSH Agent: Fix Windows agent selection, radio buttons

[hifi]

When we added support for having multiple agents enabled at the same time on Windows the unfortunate default was that no agents were enabled. This is really confusing.

Now Pageant is (again) the default and you can't create a combination that would have integration enabled but no agents.

Partially helps with #7473 but this also adds a new translation string, unfortunately.

Screenshots

Testing strategy

Quickly by hand that all positions of the radio selection were correctly saved to config file and that on first launch Pageant was selected.

Type of change

• ✅ Bug fix (non-breaking change that fixes an issue)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 64.29%. Comparing base (aca197a) to head (53d88df).
Report is 461 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #7764      +/-   ##
===========================================
- Coverage    64.31%   64.29%   -0.02%     
===========================================
  Files          339      339              
  Lines        43450    43451       +1     
===========================================
- Hits         27943    27934       -9     
- Misses       15507    15517      +10     

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