test(coordinator): rewire e2e onto shared inference-gateway and add 3-EPP topology

[revit13]

What type of PR is this?
/kind cleanup
/kind test

What this PR does / why we need it:
Reworks the coordinator e2e suite to exercise the disaggregation topologies the deployment guide (llm-d/llm-d#2119) actually ships (single-EPP and 3-EPP deployments), and drops the coordinator's private copy of the gateway manifests.

• Use the shared inference-gateway component. The suite loads EPP, InferencePool, RBAC, ServiceAccounts, and Services from deploy/components/inference-gateway/ instead of the coordinator-local epd-pool/ manifests. As in the router e2e, the coordinator fronts the EPP with a hand-rolled Envoy, so that component's gateways.yaml/httproutes.yaml stay unused.

• Consolidate the coordinator manifests. Flattens deploy/coordinator/components/coordinator/ up to deploy/coordinator/ and deletes the now-redundant manifests it replaced.

• Add an optional 3-EPP topology (E2E_EPP_TOPOLOGY=3epp). Runs one role-scoped EPP and InferencePool per phase (encode / prefill / decode), with an Envoy route that dispatches each EPP-Profile to the matching role. Each EPP sees only its own role's pods, so it uses single-profile-handler and no role filter, with per-role scorers mirroring the guide. The default single-EPP topology is unchanged.

• Extract common resources. shared-envoy-resources.yaml holds the Envoy Deployment and Service; per-topology manifests carry only the routing ConfigMap. Topology branching lives in eppsToCreate() / poolNames().

• Deploy the renderer like the router e2e. vllm-render runs as a standalone Deployment/Service, reached through the substituted ${VLLM_RENDER_URL}.

• CI. e2e-tests becomes a topology: [single, 3epp] matrix, aggregated by an e2e-tests-status job (required checks can't reference individual matrix legs).

Follow-up: a later PR will add parallelization to coordinator e2e tests, as in the router.

Which issue(s) this PR fixes:

Fixes #

Release note (write NONE if no user-facing change):

NONE