Fix `__all__` imports in `__init__.py`s

[EwoutH]

On a few places in Mesa uses __all__ imports in different __init__.pys files.

mesa/mesa/__init__.py

Lines 8 to 23 in 2cdbcb6

	import mesa.space as space
	import mesa.time as time
	from mesa.agent import Agent
	from mesa.batchrunner import batch_run
	from mesa.datacollection import DataCollector
	from mesa.model import Model
	__all__ = [
	"Model",
	"Agent",
	"time",
	"space",
	"DataCollector",
	"batch_run",
	"experimental",
	]

mesa/mesa/experimental/__init__.py

Lines 3 to 7 in 2cdbcb6

	from mesa.experimental import cell_space
	from .solara_viz import JupyterViz, Slider, SolaraViz, make_text
	__all__ = ["cell_space", "JupyterViz", "SolaraViz", "make_text", "Slider"]

This allows easier importing of modules, but does import modules that are not even necessary or used at all. This created some problems after #2265, because for some of those imports require dependencies that are not included by default.

Follow-up on #2265, fixes projectmesa/mesa-examples#198.

[invcble]

@EwoutH is this still open? I would like to work on it as a good starting point for contribution.