Revert common Py2 commit to spiir-O4-review-v3

This change should revert the changes from 655ac5bd to e3404f54

A few features and shared scripts are removed, as well as some large refactors (especially in finalsink trigger control).

For the most part the merge conflicts were simple, but finalsink & postcoh required some manual changes.

Haven't tested yet, but builds ok.

Note that we shouldn't squash commits on this one, as we want to remain in-step with the new branch py3_py2_common_branch, which performed a similar set of changes.