fix: Small fixes and test updates

[mikenairn]

Fixes a few small issues and updates the test code in preparation for future changes.

• Removes unused code/constants
• Rename variables shadowing imports names
• Update e2e test workflow to include additional env vars:
  • TEST_DNS_PROVIDER_SECRET_NAME - Name of the secret in TEST_HUB_NAMESPACE containing the provider credentials
  • TEST_DNS_ZONE_DOMAIN_NAME - DNS Provider Zone Domain Name
  • TEST_DNS_ZONE_ID - DNS Provider Zone ID
• Update e2e test workflow to dump policy and gateway logs on failure.
• Update e2e test suite to generate a domain per test suite instance i.e. t-e2e-12345.e2e.hcpapps.net. This is required to avoid multiple test runs creating the same records in the target test zone when adding wildcard entries(*.t-e2e-12345.e2e.hcpapps.net instead of *.e2e.hcpapps.net).

Some changes required for https://github.com/Kuadrant/multicluster-gateway-controller/pull/636

[mikenairn]

PR E2e Test will fail until this is merged, but has been tested here https://github.com/Kuadrant/multicluster-gateway-controller/actions/runs/7113732088/job/19366295914?pr=709

[openshift-ci[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: maleck13, mikenairn

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