sanity-check refactor

[bserem]

ddev sanity-check is growing huge really fast. It started as an experiment but it became that the benefits are many so more and more things were added to it.

We need to refactor it:

• separate pre-push requirements (like composer validate) from other checks
• limit what runs when we push to dev
• make ddev sanity-check standalone and not part of pre-push
• maybe have levels/layers?

[waako]

It's definitely doing too much.

I would normally say, split into helper scripts that get called, and I've just found we can use little helper files inside _lib folder in commands/host that won't show up in list of commands and also reusable across commands.

[bserem]

#123