fn: container initialization monitoring (#1288)

Container initialization phase consumes resource tracker
resources (token), during lengthy operations.
In order for agent stability/liveness, this phase has
to be evictable/cancelable and time bounded.

With this change, introducing a new system wide environment setting
to bound the time spent in container initialization phase. This phase
includes docker-pull, docker-create, docker-attach, docker-start
and UDS wait operations. This initialization period is also now
considered evictable.

api/server/runner_fninvoke_test.go

@@ -210,7 +210,7 @@ func TestFnInvokeRunnerExecution(t *testing.T) {
 		{"/invoke/http_stream_fn_id", multiLog, "POST", http.StatusOK, nil, "", multiLogExpectHot},
 
 		// TODO consider removing this, see comment above the image
-		{"/invoke/fail_fn", ok, "POST", http.StatusBadGateway, nil, "container exited early, please ensure", nil},
+		{"/invoke/fail_fn", ok, "POST", http.StatusBadGateway, nil, "container failed to initialize", nil},
 	}
 
 	callIds := make([]string, len(testCases))