Initial GRPC shims support

[mxpv]

• Adds a unified (TTRPC + GRPC) clients for TaskService and SandboxService.
• Shim client support
• Introduce shim bootstrap params (a JSON payload returned in stdout from Shim.Start to specify protocol, shim caps, etc).

[k8s-ci-robot]

Skipping CI for Draft Pull Request.
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[mxpv]

/test pull-containerd-sandboxed-node-e2e

[dcantah]

Approach makes sense, LGTM

[dcantah]

Minor nit after looking again, but for all of these that don't return an emptypb we should probably just return nil for the actual responses if we got an error from the original call (g.client.State in this example) to be idiomatic

[mxpv]

Once we release 1.7 and switch to v3, we can clean this code (as there will be no need to convert between v2 and v3 contracts), so it'll be a lot slimmer (like sandbox/bridge.go)

[dcantah]

Fine with me then

[dcantah]

There any plans to make registering the event service as GRPC a reality? Poorly worded, but for the go library I mean (instead of the manager registering as ttrpc always and writing the address to an env var)

containerd/runtime/v2/shim/shim.go

Lines 279 to 284 in f82ae8a

	ttrpcAddress := os.Getenv(ttrpcAddressEnv)
	publisher, err := NewPublisher(ttrpcAddress)
	if err != nil {
	return err
	}
	defer publisher.Close()

I suppose it might not even matter as this work is mainly for non-go/non-rust runtimes

[dcantah]

Just trialed this, we'll need at least grpc.WithTransportCredentials(insecure.NewCredentials()) on the dialopts for the connection otherwise you get the famed: grpc: no transport security set (use grpc.WithTransportCredentials(insecure.NewCredentials()) explicitly or set credentials)

[mxpv]

Rebased against main and fixed merge conflicts.

[dcantah]

LGTM again, dummy shim I have makes it to TaskShutdownRequest just fine if that's anything to go by 🤷