fix(filepicker): use proper folder icons

[susnux]

We need AccountGroup instead of just Group (wrong icon). Also its the key icon instead of the lock icon for encryption (to be inline with files app).

Also use outlines icons for nextcloud/server#56345

[susnux]

/backport to stable6

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 45.43%. Comparing base (e0b63a2) to head (0b19327).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2180   +/-   ##
=======================================
  Coverage   45.43%   45.43%           
=======================================
  Files          15       15           
  Lines         438      438           
  Branches       85       84    -1     
=======================================
  Hits          199      199           
  Misses        210      210           
  Partials       29       29           

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