Reinstate PR #161: Replace schedulers with AgentSet functionality

[EwoutH]

This reinstates PR #161 after the previous revert in #170.

Now that projectmesa/mesa#2223 is merged, these examples are fully functional again without schedulers.

Original description of #161 below.

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This PR replace all the RandomActivation and SimultaneousActivation schedulers used in the example models with AgentSet functionality. This simplifies models and allows for easier and more flexible modification of these models. It algins the examples with the current best practices in Mesa.

RandomActivation

The RandomActivation schedulers were removed, and in the Model.step() function the schedule step was replaced with an AgentSet operation, like:

-        self.schedule.step()
+        self.agents.shuffle().do("step")

The following RandomActivation schedulers were removed:

• bank_reserves
• boid_flockers
• boltzmann_wealth_model
• boltzmann_wealth_model_experimental
• boltzmann_wealth_model_network
• caching_and_replay
• charts
• el_farol
• epstein_civil_violence
• forest_fire
• hotelling_law
• schelling
• shape_example
• virus_on_network

SimultaneousActivation

To remove the SimultaneousActivation schedulers, the Agent methods were renamed from step() and advance() to more descriptive functions. The model step was updated accordingly:

-        self.schedule.step()
+        self.agents.do("determine_state")
+        self.agents.do("assume_state")

The following SimultaneousActivation schedulers were removed:

• hex_snowflake
• color_patches
• conways_game_of_life

Relevant tickets

• Use new AgentSet functionality in examples #111
• Deprecate all schedulers and be free to do whatever you want mesa#1912
• Introduce AgentSet class mesa#1916
• model: Automatically increase steps counter mesa#2223

[EwoutH]

Test function exactly as expected: Since #2223 is not in the latest pre-release, that's supposed to fail. The main branch passes also as expected.