chore(cmd): clean up commands (#9705)

Move infrastructure related commands to under `cmd/infra` and
development stuff to `cmd/dev`. The default build command builds the
regular user facing binaries: syncthing, stdiscosrv, and strelaysrv.

cmd/infra/strelaypoolsrv/auto/.gitignore

@@ -0,0 +1 @@
+gui.files.go

cmd/infra/strelaypoolsrv/auto/doc.go

@@ -0,0 +1,10 @@
+// Copyright (C) 2018 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+//go:generate go run ../../../../script/genassets.go -o gui.files.go ../gui
+
+// Package auto contains auto generated files for web assets.
+package auto

cmd/infra/strelaypoolsrv/auto/noassets.go

@@ -0,0 +1,16 @@
+// Copyright (C) 2021 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+//go:build noassets
+// +build noassets
+
+package auto
+
+import "github.com/syncthing/syncthing/lib/assets"
+
+func Assets() map[string]assets.Asset {
+	return nil
+}