feat: refactor kargo events

[gdsoumya]

This PR :

1. Fixes small bit of promotion reconciler cleanup #1851
2. Adds freight creation time to all promotion/freight events

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[codecov]

Codecov Report

Attention: Patch coverage is 38.88889% with 11 lines in your changes are missing coverage. Please review.

Project coverage is 46.14%. Comparing base (5287d0e) to head (d38508e).

Files	Patch %	Lines
internal/controller/promotions/promotions.go	9.09%	9 Missing and 1 partial ⚠️
api/v1alpha1/event.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1853      +/-   ##
==========================================
+ Coverage   46.11%   46.14%   +0.03%     
==========================================
  Files         213      213              
  Lines       13873    13865       -8     
==========================================
+ Hits         6397     6398       +1     
+ Misses       7191     7183       -8     
+ Partials      285      284       -1     

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