tickets/DM-46157: Move Nublado Client into Nublado monorepo

[athornton]

This combines the features of the somewhat-diverged Mobu and Noteburst clients, and moves the whole thing into the Nublado monorepo.

Ghostwriter is the only current customer, and I imagine we will find some bugs as we rework Mobu and Noteburst to use the unified client. More with Noteburst, most likely, since this is very close to the Mobu client.

[jonathansick]

Most of the comments are ideas/suggestions, but the critical one that needs to be fixed is putting the dependencies in pyproject.toml and dropping the requirements/main.txt file.

[athornton]

Except I hadn't pushed that pyproject.toml update.