events: rename AnnouncementType to Kind

[shashankram]

Description:
Renames the type to so that it reads better when
used by other pkgs - announcements.Kind vs
announcements.AnnouncementType.

Affected area:

Functional Area
Control Plane	[X]

Please answer the following questions with yes/no.

1. Does this change contain code from or inspired by another project? no

   • Did you notify the maintainers and provide attribution?

2. Is this a breaking change? no

[codecov-commenter]

Codecov Report

Merging #4152 (76f939d) into main (d81ba22) will increase coverage by 0.04%.
The diff coverage is 71.15%.

@@            Coverage Diff             @@
##             main    #4152      +/-   ##
==========================================
+ Coverage   69.45%   69.49%   +0.04%     
==========================================
  Files         212      212              
  Lines       11429    11429              
==========================================
+ Hits         7938     7943       +5     
+ Misses       3438     3433       -5     
  Partials       53       53              

Flag	Coverage Δ
unittests	69.49% <71.15%> (+0.04%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pkg/catalog/dispatcher.go	36.66% <0.00%> (ø)
...certificate/providers/vault/certificate_manager.go	63.06% <0.00%> (ø)
pkg/configurator/client.go	84.80% <66.66%> (ø)
pkg/ticker/ticker.go	90.00% <71.42%> (ø)
...icate/providers/certmanager/certificate_manager.go	85.13% <100.00%> (ø)
...ertificate/providers/tresor/certificate_manager.go	83.47% <100.00%> (ø)
pkg/envoy/registry/announcement_handlers.go	80.00% <100.00%> (ø)
pkg/envoy/registry/services.go	95.40% <100.00%> (ø)
pkg/k8s/event_handlers.go	94.44% <100.00%> (ø)
pkg/k8s/events/event_pubsub.go	100.00% <100.00%> (ø)
... and 1 more

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[draychev]

massive!