Introduce drop-account capability

[ZetaTom]

This change introduces the drop-account capability required by nextcloud/android#11950. The corresponding server-side plug-in change is documented here.

[codecov]

Codecov Report

Merging #1213 (26c1139) into master (475f478) will decrease coverage by 0.05%.
Report is 2 commits behind head on master.
The diff coverage is 16.66%.

❗ Current head 26c1139 differs from pull request most recent head 9c7ffe3. Consider uploading reports for the commit 9c7ffe3 to get more accurate results

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1213      +/-   ##
============================================
- Coverage     52.51%   52.46%   -0.05%     
+ Complexity      973      972       -1     
============================================
  Files           189      189              
  Lines          6970     6976       +6     
  Branches        914      916       +2     
============================================
  Hits           3660     3660              
- Misses         2802     2806       +4     
- Partials        508      510       +2     

Files	Coverage Δ
...cloud/android/lib/resources/status/OCCapability.kt	93.54% <100.00%> (+0.10%)	⬆️
...sources/status/GetCapabilitiesRemoteOperation.java	51.29% <0.00%> (-0.85%)	⬇️

... and 3 files with indirect coverage changes

[github-actions]

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[tobiasKaminsky]

/rebase

[nextcloud-android-bot]

master-IT test failed: https://www.kaminsky.me/nc-dev/library-integrationTests/2244-IT-master-09-55/debug/