Draft: Migrate core functionality from partytown_drupal

This MR is an attempt to combine the two existing PartyTown modules together so we can use only the partytown namespace moving forward.

Currently, this includes the core functionality and schema from partytown_drupal, plus a little bit of glue-code to fit the current paradigm of the partytown module.

Marked as a draft because I'd like to do some more testing and refining, but I think the core of it is worth discussing and reviewing early to make sure we're aligned and headed in the right direction.