This PR is the first step to improve and rationalize the life-cycle of a pyscript app along the lines of what I described in #763 .
It is not a complete solution, more PRs will follow.
Highlights:
- py-config is no longer a web component: the old code relied on PyConfig.connectedCallback to do some logic, but then if no <py-config> tag was present, we had to introduce a dummy one with the sole goal of activating the callback. Now the logic is much more linear.
- the new pyconfig.ts only contains the code which is needed to parse the config; I also moved some relevant code from utils.ts because it didn't really belong to it
- the old PyConfig class did much more than dealing with the config: in particular, it contained the code to initialize the env and the runtime. Now this logic has been moved directly into main.ts, inside the new PyScriptApp class. I plan to refactor the initialization code in further PRs
- the current code relies too much on global state and global variables, they are everywhere. This PR is a first step to solve the problem by introducing a PyScriptApp class, which will hold all the mutable state of the page. Currently only config is stored there, but eventually I will migrate more state to it, until we will have only one global singleton, globalApp
- thanks to what I described above, I could kill the appConfig svelte store: one less store to kill :).
