e2e: cover egress on grpc requests and bidi streaming

[yufan-su]

Add an e2e test to cover egress on sending grpc requests and bidi streaming in it.

What's here

• internal/proto/grpcechopb — a small Echo service with one method per streaming shape: unary Echo, server-streaming EchoStream, bidirectional EchoBidi. Generated files checked in, per the convention in the neighbouring proto packages.

• internal/e2e/fixtures/grpcecho — the origin: a cleartext-HTTP/2 server, no TLS anywhere, with the standard health service so the pod can use a grpc readinessProbe and nothing between the actor and the origin parses HTTP. Pod + Service template, deployed per test into the suite's namespace.

• demos/egress — the actor gains POST /grpc, which dials the target and runs whichever RPCs the request asks for. It dials per request and closes with it: the actor is checkpointed and restored, and an HTTP/2 connection opened before a snapshot does not survive one. The gRPC status comes back as a string rather than being flattened into the HTTP status, since that status is the trailer assertion.

• internal/e2e/suites/networking/grpcegress_test.go — TestActorEgressGRPC drives all three shapes through nftables REDIRECT → atunnel → atenet-egress → origin, then asserts the gateway's access log recorded the CONNECT for that actor's certificate. Without that last check everything above would also pass on masqueraded traffic that never reached the gateway.

• Tests pass

• Appropriate changes to documentation are included in the PR

[haiyanmeng]

grpcegress_test.go:161-239 duplicates sdsmint_test.go:352-437:

• startGRPCEcho ≈ startProbe
• waitForGRPCEchoReady ≈ waitForProbeReady
• describeGRPCEchoState:226 is identical to describeProbeState apart from the loop variable name

[haiyanmeng]

This one seems mostly duplicate with internal/e2e/fixtures/egressprobe/egressprobe.yaml.tmpl. Can we reuse it somehow to reduce duplication?

[haiyanmeng]

yufan-su thanks for the work.

Can you take a look across this PR, #1054, and the existing test code, to figure out a solution minimizing the duplication in our test code?