chore: split config change detector into gw and konnect flavor

[czeslavo]

What this PR does / why we need it:

Splits the DefaultConfigChangeDetector into KongGatewayConfigChangeDetector and KonnectConfigChangeDetector. As they are now used by two separate components (KongClient and konnect.ConfigSynchronizer), we can remove the client.IsKonnect() conditional from the detector and rely on the dependency injection.

Which issue this PR fixes:

Part of #6340.

[codecov]

Codecov Report

Attention: Patch coverage is 72.72727% with 3 lines in your changes missing coverage. Please review.

Project coverage is 76.9%. Comparing base (40d909f) to head (b43fc2c).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/manager/setup.go	0.0%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #6942     +/-   ##
=======================================
+ Coverage   76.7%   76.9%   +0.1%     
=======================================
  Files        214     214             
  Lines      25139   25169     +30     
=======================================
+ Hits       19299   19371     +72     
+ Misses      4825    4779     -46     
- Partials    1015    1019      +4     

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