refactor: refactor Gateway API's route parent status update code

[pmalek]

What this PR does / why we need it:

Refactor route parent status handling for Gateway API routes. This extract code from ensureGatewayReferenceStatusAdded from all the route controllers and adds common functions based on implementation ensureGatewayReferenceStatusAdded into internal/controllers/gateway/route_parent_status.go.

Which issue this PR fixes:

Special notes for your reviewer:

PR Readiness Checklist:

Complete these before marking the PR as ready to review:

• the CHANGELOG.md release notes have been updated to reflect any significant (and particularly user-facing) changes introduced by this PR

[codecov]

Codecov Report

Attention: Patch coverage is 94.69027% with 12 lines in your changes missing coverage. Please review.

Project coverage is 76.8%. Comparing base (6ca4eee) to head (3a7b01e).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...ternal/controllers/gateway/grpcroute_controller.go	0.0%	6 Missing ⚠️
...nternal/controllers/gateway/udproute_controller.go	0.0%	6 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #6877     +/-   ##
=======================================
+ Coverage   76.5%   76.8%   +0.2%     
=======================================
  Files        212     214      +2     
  Lines      25246   25139    -107     
=======================================
- Hits       19321   19308     -13     
+ Misses      4912    4814     -98     
- Partials    1013    1017      +4     

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[randmonkey]

Almost LGTM, some minor comments.