fix: handing GRPCRoute hostname from Gateway

[tao12345666333]

What this PR does / why we need it:

There is a test case in the conformance test of GWAPI where hostname is not specified in GRPCRoute, but it is specified in Gateway. Therefore, when routing requests, the configuration for hostname needs to be obtained from Gateway and routes need to be generated accordingly so that request proxying can proceed normally.

Which issue this PR fixes:

fixes: #6136

Special notes for your reviewer:

This can be seen as a fix to the existing logic, or it can be seen as a feature enhancement. However, there won't be too much of a noticeable difference for users, so I didn't add it to the CHANGELOG.

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

[tao12345666333]

When delving into the details, I found that KIC did not cover this case in the processing logic of HTTPRoute.
Perhaps we should also add similar processing logic for HTTPRoute?

[pmalek]

The enabled test seems to fail:

https://github.com/Kong/kubernetes-ingress-controller/actions/runs/9417299955/job/25942276779

2024-06-07T12:58:47.7558580Z     --- FAIL: TestGatewayConformance/GRPCExactMethodMatching (0.02s)
2024-06-07T12:58:47.7559692Z         --- PASS: TestGatewayConformance/GRPCExactMethodMatching/2_request_to_'/gateway_api_conformance.echo_basic.grpcecho.GrpcEcho/EchoThree'_should_receive_a_Unimplemented_(12) (0.01s)
2024-06-07T12:58:47.7560846Z         --- PASS: TestGatewayConformance/GRPCExactMethodMatching/0_request_to_'/gateway_api_conformance.echo_basic.grpcecho.GrpcEcho/Echo'_should_go_to_grpc-infra-backend-v1 (3.25s)
2024-06-07T12:58:47.7561992Z         --- FAIL: TestGatewayConformance/GRPCExactMethodMatching/1_request_to_'/gateway_api_conformance.echo_basic.grpcecho.GrpcEcho/EchoTwo'_should_go_to_grpc-infra-backend-v2 (30.00s)

[tao12345666333]

The enabled test seems to fail:

https://github.com/Kong/kubernetes-ingress-controller/actions/runs/9417299955/job/25942276779

This is because my current branch has not yet merged the latest changes in the main branch. ac6a0d8 (I skipped that case.)

I have already rebased.

[codecov]

Codecov Report

Attention: Patch coverage is 74.19355% with 8 lines in your changes missing coverage. Please review.

Project coverage is 73.7%. Comparing base (74f527d) to head (9c53ba2).
Report is 6 commits behind head on main.

Files	Patch %	Lines
...al/dataplane/translator/subtranslator/grpcroute.go	73.3%	6 Missing and 2 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #6166     +/-   ##
=======================================
- Coverage   73.7%   73.7%   -0.1%     
=======================================
  Files        198     198             
  Lines      19724   19767     +43     
=======================================
+ Hits       14547   14578     +31     
- Misses      4196    4204      +8     
- Partials     981     985      +4     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.