fix: Set operation state to nil if new operation has been initiated by a direct object update (#20875)

[andrii-korotkov-verkada]

Fixes #20875

Some systems like Kargo update the application operation directly to initiate a new sync, bypassing the server. However, they can't update the status operation state to become nil, resulting in discrepancy, see akuity/kargo#2985 and the discussion. Handle this case on the app controller side.

Let's cherry-pick to v2.13.

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[andrii-korotkov-verkada]

According to @stephaneetje testing, this indeed fixes the issues with old sync information being shown and app out of sync.

[codecov]

Codecov Report

Attention: Patch coverage is 60.00000% with 10 lines in your changes missing coverage. Please review.

Project coverage is 54.98%. Comparing base (32cc663) to head (bb5db09).
Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
controller/appcontroller.go	52.38%	7 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #20915      +/-   ##
==========================================
- Coverage   55.04%   54.98%   -0.06%     
==========================================
  Files         324      324              
  Lines       55421    55480      +59     
==========================================
+ Hits        30504    30505       +1     
- Misses      22303    22347      +44     
- Partials     2614     2628      +14     

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