[TF2] Add support for Arena mode in TF bots

[Blixibon]

This PR adds support for Arena mode to bots in TF2. Bots will initially use their seek and destroy AI, and then they will attempt to capture the point once it is unlocked. Medics and engineers abort their default AI if they are the last members of their team.

This depends on two other otherwise standalone features:

• A fix for spawn room incursion distances not being calculated when there is no func_respawnroom in the level.
• An upstream PR which fixes seek and destroy AI when there is no objective. (I think this might be mostly unnecessary, although the time remaining fix may be needed)

Bots are supported with or without the queue enabled.

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PR Checklist

• My PR follows all guidelines in the CONTRIBUTING.md file
• My PR targets a develop branch OR targets another branch with a specific goal in mind