Remove plugin system

[codefiles]

Closes #3021

[svartkanin]

Fine by me, but I'll await @Torxed opinion

[Torxed]

Need to consider this a bit. It breaks a few known users use cases, mine included.

Is it just in favor of removing code that otherwise looks unused? Or just to clean up complexity?

[h8d13]

think yes it's a lot of complexity in main installer file

We could also document to make modification into guided.py at the stage they need with some things that can help them to do this properly like installation.something and profile.provision or post_install probably a few more that are easier to play with properly

[codefiles]

Maybe removing it is not the way to go.

[svartkanin]

If it is broken but still serves a purpose then there is the option to remove it and introduce a reworked version that is more aligned with the current state of archinstall (the plugin system was introduced a long time ago where the installer was not as flexible and library driven). The other option is the keep it and fix it, if it fits into the current structure and model of the code.

To me the word plugin sounds a bit more like "apps" and not what it actually does which are hooks during the installation. So maybe re-branding it to installation hooks may be better?

If it is broken right now and does not provide any value then removing it is probably the right way forward.