Move firebase deployment prep location

Move firebase deployment preparation location form

firebase/public -> out/firebase/public

Rationale: firebase/public is generated, but firebase/*.json etc. are tracked - this is confusing. Also: typically generated, untracked files sit in /out. Additionally we currently copy files from /frontend to /out/public and then to /firebase/public - these three locations have thrown me a few times now, let's just use two:

source (frontend) and
stage (out/firebase/stage).

Relevant firebase configs should be copied to out/firebase prior to running firebase-deploy, so that config and generated static code is all contained in the one directory.

The out/public location was initially created as I expected to be using webpack or rollup to bundle frontend. However, I have now decided to try and avoid any bundling and building.

There are still a couple of files in /frontend that are generated (ie not handwritten, not true source and not tracked in git):

wasm_exec.js (copied from tinygo env)
evy.wasm (built with tinygo)

Still a little ugly but necessary in order to run servedir on /frontend. We should keep with this slightly ugly pattern and move version.json creation to target /frontend.

evylang / todo

Move firebase deployment prep location #47