make a plan for cleaning up c-tor debian packaging

at the TPA meetup, we discussed a possible way forward to cleanup the Debian packaging of legacy tor, AKA c-tor, little-t-tor, etc.

there, i suggested we do the following:

1. merge (MR) the resulting debian/ directory from the generated source package to the upstream tpo/core/tor git repository
2. hook package build into that repo's CI (see also Trigger automated build of new debian packages ... (#42332))
3. have CI upload the package to a "proposed updates" suite of some sort on deb.tpo
4. archive the multitude of old git repos used for the debian package
5. upload a real package to sid, changing maintainership
6. wait for testing to upload to backports or upload to fasttrack

We need to make a proper proposal for all of this so that people are looped in.

@lavamind / @lelutin any of you two want to carry this, or should i be working on the proposal?

note that this was generally approved by @weasel, see #42216 for details of that conversations.

this only covers little-c-tor, not the entirety of the deb.tpo service, which also needs more thinking about (e.g. what do we do with the other issues described in #42216).