Delegate shinylive deployment to code in shinylive

[wch]

This PR makes it so that when shiny static is called, it runs code provided by the shinylive bundle. This makes it so that shinylive can make changes to how it does deployment, without having to synchronize it with the shiny package.

Along with posit-dev/py-shinylive#14, it also makes the following possible:

---

Multiple applications can be deployed in one command, with:

shiny static app1 site --subdir a1
shiny static app2 site --subdir a2
shiny static app3 site --subdir a3

This will create the following directory structure:

site
├── a1
│   ├── app.json
│   ├── edit
│   │   └── index.html
│   └── index.html
├── a2
│   ├── app.json
│   ├── edit
│   │   └── index.html
│   └── index.html
├── a3
│   ├── app.json
│   ├── edit
│   │   └── index.html
│   └── index.html
├── serviceworker.js
└── shinylive     # Other JS stuff in here, including pyodide

All of the deployed apps share the same shinylive resources.

Note that if you want one to be deployed to the top level, it can be done by just not using --subdir:

shiny static app1 site
shiny static app2 site --subdir a2

site
├── app.json   # Top level application, from source dir app1/
├── edit
│   └── index.html
├── index.html
├── a2
│   ├── app.json
│   ├── edit
│   │   └── index.html
│   └── index.html
├── serviceworker.js
└── shinylive

---

shiny static now by default only includes packages needed to run the deployed application(s). Previously, a deployment would be about 200MB because it included all of the packages from Pyodide, as well as a few other shiny-related packages. With the change in posit-dev/py-shinylive#14, a minimal shinylive app deployment is now about 27MB.

If deployed this way, then when a user goes to the /edit/ page and makes changes or runs code in the terminal, they will not be able to load any extra packages that normally are part of the distribution (they will be able to load packages from PyPI, but as always, these packages must not contained any compiled code).

In order to include the full Shinylive distribution, the option --full-shinylive can be used.