Add missing functionality to tools/stresser

[rj00a]

The stresser is missing some features. The PR that added the tool was merged a bit too hastily and some essential functionality was left out. In particular, the fake clients just stand at the spawn point without moving.

Ideally, the tool should behave almost the same as rust-mc-bot with clients running around and performing other actions. See this.

Blocked on #348

[dyc3]

I think this should be split into 2 separate issues.

[qualterz]

I think this should be split into 2 separate issues.

The first issue could be called like "Upstream stresser tool", and the second like "Stresser bots random actions".

[rj00a]

I think this should be split into 2 separate issues.

Done.