Use new AgentSet functionality in examples

_Open for contributions!_

I would like some example to use the now stabilized AgentSet. This means sometimes self.schedule.agents can be replaced, and sometimes the scheduler could be removed all together. See:

- Original PR: https://github.com/projectmesa/mesa/pull/1916
- Current docs: https://mesa.readthedocs.io/en/stable/mesa.html#mesa.agent.AgentSet
- Source code: https://github.com/projectmesa/mesa/blob/main/mesa/agent.py#L83
- Original discussion: https://github.com/projectmesa/mesa/discussions/1912

The approach for this would generally be:

- Read up on AgentSet functionality
- Go through the Mesa examples and seek oppertunities where the AgentSet could simplify or improve things.
- Open a Discussion on mesa-examples proposing your changes
- Implement them and open a PR here

The nuance here being that applying the AgentSet is not a goal to be implemented as much as possible, but a means that could make some model (parts) more elegant, efficient, readable and/or performant.

Read the AgentSet documentation and mesa/agent.py#L83, then review the Mesa examples for opportunities to replace self.schedule.agents or remove schedulers. Propose candidate changes in a mesa-examples Discussion before implementing them; done means the agreed example updates are implemented and a PR is opened.

Written by the indexing model from the issue text.