Deduplication of installer code

@oopsbagel has started abstracting the installer away here: https://github.com/efforg/rayhunter/blob/3239daa01110fba6b5f5c2359e4f0cefbaad2f10/installer/src/pinephone.rs#L178-L181

This issue is to track that effort and also discuss what we could solve with this.

Some ideas off the top of my head:

* Currently every installer has to carry its own "dev utils". There is a `util` command for every device that is somehow supposed to launch a shell, and they all work slightly differently.
* Likewise, some devices have tool commands to copy files and others don't.
* As a result of this, we have `make.sh` which only works for Orbic and maybe some other devices. It would be nice to have the installer abstracted far enough to allow a make.sh that works for everybody.