Objective Assignment Refactor

[Elijahrane]

About the PR

Fixes a few issues:

1. the 'prob' field sucks and is misleading
2. it's hard to keep track of all of the objective probs without similar objectives grouped, leading to way too many steal objectives. Now they're all in a central place and it's easy to make adjustments
3. we needed some ground laid for changeling, wizard, crew, etc objectives. Now you can just specify which group of objectives you want to pick from and it's in yaml.

Changelog

:cl: Rane

• tweak: Traitor objectives should no longer be overly steal-oriented.
• fix: The fallback for the 'keep another traitor alive' condition now just gives you stay alive rather than telling you to keep yourself alive.

[Elijahrane]

As a note for local testing, admin menu traitors have super broken condition detection (not something this pr changed) so for local testing I recommend running a few clients with players_per_traitor set to 1 in traitor mode (which has to start in secret because of https://github.com/space-wizards/space-station-14/issues/8952

[civilCornball]

yessss, finally

way too many steal objectives (though they usually end up as ‘kill the Head that has this’ objectives)

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[github-actions[bot]]

This pull request has conflicts, please resolve those before we can evaluate the pull request.