fix: httproute should enqueue requests when gateways are deleted

[jonstacks]

What

While working on #658, I found a bug where we weren't triggering a reconcile for httproutes when one of their parentRef gateways changed. When the gateway was deleted, it wasn't reflecting in the http route status conditions properly.

How

• In the HTTPRoute reconciler, create a watch on gateways and when one changes, find all http routes that reference that gateway and trigger a reconcile for them.
• Reduce the timeout in the httproute test. This was originally bumped while I couldn't figure out why the test was flakey. Now that we correctly reconcile on gateway deletions, we can move the timeout back down to a lower value.

Breaking Changes

No

[Copilot]

Pull Request Overview

This PR ensures HTTPRoutes are reconciled when their parent Gateways change (including deletions) and restores a lower, consistent timeout in tests.

• Added a watch on Gateway resources to enqueue affected HTTPRoutes via findHTTPRouteForGateway.
• Introduced findHTTPRouteForGateway mapping function that lists HTTPRoutes referencing the changed Gateway.
• Updated the HTTPRoute controller test to use the shared timeout variable instead of a hardcoded 30s.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
internal/controller/gateway/httproute_controller.go	Added Gateway watch & mapping, adjusted validation error handling
internal/controller/gateway/httproute_controller_test.go	Switched test from hardcoded 30s to shared timeout variable

[codecov]

Codecov Report

Attention: Patch coverage is 47.54098% with 32 lines in your changes missing coverage. Please review.

Project coverage is 30.85%. Comparing base (cbe6362) to head (09fd888).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...nternal/controller/gateway/httproute_controller.go	47.54%	28 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #660      +/-   ##
==========================================
+ Coverage   30.83%   30.85%   +0.01%     
==========================================
  Files         101      101              
  Lines       15925    15984      +59     
==========================================
+ Hits         4911     4932      +21     
- Misses      10729    10762      +33     
- Partials      285      290       +5     

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