FrontendService: Local dev setup (#108082)

* wip

* docker compose dev setup

* commit new tilt stuff

* move files into own dir

* reset files back to main

* use just one nginx container for both gateway and cdn

* update proxy service name

* make it all work when in subdir

* rename more things

* reset more changes

* fix config

* add makefile command, fix ws upgrade

* add local check script

* tidy

* tidy up, comments, readyme

* codeowners

* change cdn host to localhost to avoid adding host.docker.internal to /etc/hosts

* route POST /login to backend

* Build nginx container with config baked in so it can be live_update-ed

* fix headers

.github/CODEOWNERS

@@ -305,6 +305,7 @@
 /devenv/jsonnet/ @grafana/dataviz-squad
 /devenv/local_cdn/ @grafana/frontend-ops
 /devenv/local-npm/ @grafana/frontend-ops
+/devenv/frontend-service/ @grafana/grafana-frontend-platform
 /devenv/setup.sh @grafana/grafana-backend-services-squad
 /devenv/plugins.yaml @grafana/plugins-platform-frontend