fix: aggregate xRoute/xPolicy statuses across GWCs in gateway-api runner

[y-rabie]

First PR split of #7307. Includes only changes in the gateway-api runner.
E2e tests are included in the second PR.

[codecov]

Codecov Report

❌ Patch coverage is 10.61947% with 202 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.06%. Comparing base (4af9a89) to head (e5e5925).

Files with missing lines	Patch %	Lines
internal/gatewayapi/runner/runner.go	0.00%	196 Missing ⚠️
internal/gatewayapi/extensionserverpolicy.go	80.00%	2 Missing and 4 partials ⚠️

❌ Your patch check has failed because the patch coverage (10.61%) is below the target coverage (60.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7557      +/-   ##
==========================================
- Coverage   72.28%   72.06%   -0.22%     
==========================================
  Files         232      232              
  Lines       34152    34289     +137     
==========================================
+ Hits        24688    24712      +24     
- Misses       7684     7796     +112     
- Partials     1780     1781       +1     

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[arkodg]

hey @y-rabie I agree with the overall logic here, suggesting improvements in the algo to avoid the nested for loops

• can replace the .Store with an internal Merge
• common state can be stored in map with status ptr as values