BUILDS ON #44344. Please review that one first.

Commit Message

Add integration tests and examples for reverse tunnel reporter

Additional Description

Adds end-to-end integration tests and usage examples for the reverse tunnel reporting system introduced in the prior PRs (#44327, #44342, #44344).

Integration tests:

• GrpcClientIntegrationTest: spins up a full Envoy instance with the reverse tunnel bootstrap extensions and a real gRPC test server. Validates the complete flow: reverse tunnel establishment triggers connection events through the EventReporter
  new connections made using lds.
• Test cases cover happy path, multi-listener fan-out, disconnect handling, reconnect with full push, and a release-only load test.

Examples:

• responder-reporter-envoy.yaml: reference Envoy config showing how to wire the reporter and gRPC client into the upstream socket interface bootstrap extension.
• test_server.cc: minimal standalone gRPC server that receives and prints tunnel reports, useful for manual validation and as a sample for others developing servers targeting this feature.

Also fixes the call from the reverse_tunnel_filter to the reporting when done with tenant_isolation.

Risk Level: Low

Testing

Integration tests, example config.

Request variables

Key	Value
ref	0df27a3
sha	6437b5b
pr	44345
base-sha	72fe53c
actor	@aakugan
message	Add integration tests and examples for reverse tunnel reporter...
started	1775722568.807303
target-branch	main
trusted	false

Container image/s (as used in this CI run)

Envoy version (as used in this CI run)