[devbin] Local UI development proxy server

[daniel-goldstein]

This adds a script that runs an aiohttp server on localhost that by default proxies all requests to whatever batch namespace hailctl is pointed to but serves static assets and renders all HTML locally. This allows for local editing of HTML / CSS / SCSS files.

To run, this branch needs to be deployed in the relevant namespace (to pick up the changes to web_common.py), and you need to have the sass CLI installed (brew install sass/sass/sass). Then run in a separate terminal make devserver SERVICE=batch and open up localhost:8000. If you want to supply fake data instead of proxying an endpoint to the k8s deployment of the service, you can override that endpoint in dev_proxy.py.

If this looks good, I'll add the above instructions to the dev docs.

Resolves #13629

[daniel-goldstein]

@iris-garden bump

[daniel-goldstein]

@iris-garden bump. It's a bit tedious to keep resolving the requirements conflicts

[danking]

WIP until I get things merged

[iris-garden]

@daniel-goldstein sorry for the slow review turnaround! the code looks good to me, and i'll try it out tomorrow morning to make sure i don't have any additional feedback. thanks!

[iris-garden]

to be included in the dev docs:

the devserver uses the default_namespace configured via hailctl dev config, so make sure to change that to your dev namespace or the default namespace as desired

whatever service you're trying to hack on the UI of needs to be pip installed, as well as web_common and gear; for example, pip install -e web_common gear batch