Load testing: synthetic VMs, multiple worker support and Grafana k6 test (#389)

* Load testing: synthetic VMs, multiple worker support and Grafana k6 test

* echoserver: prevent fallthrough when Accept() fails

* Move default local-dev context logic to CreateDevController()

* Synthetic: add a random delay to startup script echoing

go.mod

@@ -26,6 +26,7 @@ require (
 	github.com/pkg/errors v0.9.1
 	github.com/prometheus/client_golang v1.23.2
 	github.com/pterm/pterm v0.12.82
+	github.com/puzpuzpuz/xsync/v4 v4.0.0
 	github.com/samber/lo v1.52.0
 	github.com/samber/mo v1.16.0
 	github.com/sethvargo/go-password v0.3.1
@@ -42,6 +43,7 @@ require (
 	golang.org/x/crypto v0.47.0
 	golang.org/x/exp v0.0.0-20250218142911-aa4b98e5adaa
 	golang.org/x/net v0.49.0
+	golang.org/x/sync v0.19.0
 	golang.org/x/term v0.39.0
 	google.golang.org/grpc v1.78.0
 	google.golang.org/protobuf v1.36.11
@@ -123,7 +125,6 @@ require (
 	github.com/prometheus/client_model v0.6.2 // indirect
 	github.com/prometheus/common v0.66.1 // indirect
 	github.com/prometheus/procfs v0.16.1 // indirect
-	github.com/puzpuzpuz/xsync/v4 v4.0.0 // indirect
 	github.com/rivo/uniseg v0.4.7 // indirect
 	github.com/spf13/pflag v1.0.9 // indirect
 	github.com/tklauser/go-sysconf v0.3.16 // indirect
@@ -142,7 +143,6 @@ require (
 	go.yaml.in/yaml/v2 v2.4.2 // indirect
 	go.yaml.in/yaml/v3 v3.0.4 // indirect
 	golang.org/x/arch v0.16.0 // indirect
-	golang.org/x/sync v0.19.0 // indirect
 	golang.org/x/sys v0.40.0 // indirect
 	golang.org/x/text v0.33.0 // indirect
 	google.golang.org/genproto v0.0.0-20230410155749-daa745c078e1 // indirect