test: added integration test on HTTPS

[mlavacca]

What this PR does / why we need it:

a new Integration test on HTTPRoute with HTTPS traffic has been added

Which issue this PR fixes

Fixes #87

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 significant changes

[mlavacca]

@czeslavo I factorized a lot of code between the two HTTPRoute tests, PTAL

[czeslavo]

Nice refactor!

[pmalek]

Tests are failing

=== FAIL: test/integration TestIntegration/TestGatewayEssentials (29.31s)
    test_gateway.go:36: performing test setup
    test_gateway.go:36: creating a testing namespace
    test_gateway.go:36: using test namespace: cf23a136-587d-4eb9-89be-9ce685693de6
    test_gateway.go:38: deploying a GatewayClass resource
    test_gateway.go:41: 
        	Error Trace:	/home/runner/work/gateway-operator/gateway-operator/test/integration/test_gateway.go:41
        	Error:      	Received unexpected error:
        	            	GatewayClass.gateway.networking.k8s.io "8bc82141-0e42-4437-8458-9c65ccaf964a" is invalid: [spec.parametersRef.kind: Invalid value: "": spec.parametersRef.kind in body should be at least 1 chars long, spec.parametersRef.name: Invalid value: "": spec.parametersRef.name in body should be at least 1 chars long]
        	Test:       	TestIntegration/TestGatewayEssentials
W0422 09:41:35.403238   15594 warnings.go:70] unknown field "spec.controlPlaneOptions.deployment.podTemplateSpec.metadata.creationTimestamp"

[mlavacca]

Tests are failing

=== FAIL: test/integration TestIntegration/TestGatewayEssentials (29.31s)
    test_gateway.go:36: performing test setup
    test_gateway.go:36: creating a testing namespace
    test_gateway.go:36: using test namespace: cf23a136-587d-4eb9-89be-9ce685693de6
    test_gateway.go:38: deploying a GatewayClass resource
    test_gateway.go:41: 
        	Error Trace:	/home/runner/work/gateway-operator/gateway-operator/test/integration/test_gateway.go:41
        	Error:      	Received unexpected error:
        	            	GatewayClass.gateway.networking.k8s.io "8bc82141-0e42-4437-8458-9c65ccaf964a" is invalid: [spec.parametersRef.kind: Invalid value: "": spec.parametersRef.kind in body should be at least 1 chars long, spec.parametersRef.name: Invalid value: "": spec.parametersRef.name in body should be at least 1 chars long]
        	Test:       	TestIntegration/TestGatewayEssentials
W0422 09:41:35.403238   15594 warnings.go:70] unknown field "spec.controlPlaneOptions.deployment.podTemplateSpec.metadata.creationTimestamp"

It's fixed now

[pmalek]

Minor nits which I do not consider blockers for this PR. 👍