update code to compatible with brainstate>=0.1.0

[chaoming0625]

This pull request includes significant refactoring and renaming of classes and methods in the dendritex module, along with some additional functionality. The most important changes include the renaming of DendriticDynamics to DendriteDynamics, the removal of the DendriticDynamics class, and the simplification of various methods and class definitions.

Class and method renaming and refactoring:

• dendritex/_base.py: Renamed DendriticDynamics to DendriteDynamics and removed the DendriticDynamics class. Refactored the DendriteDynamics class to inherit from bst.mixin.Mixin and simplified its methods.
• dendritex/_base.py: Updated HHTypedNeuron, IonChannel, and MixIons classes to inherit from the new DendriteDynamics class and refactored their methods accordingly. [1] [2] [3]

Simplification of method signatures and logic:

• dendritex/_base.py: Simplified the _format_elements method in the Container class by removing support for tuple-typed components and only accepting dictionary-typed components.
• dendritex/_base.py: Refactored add_elem methods to remove support for tuple-typed elements and only accept dictionary-typed elements. [1] [2] [3]

Additional functionality:

• dendritex/_integrators.py: Added new integration methods midpoint_step, heun2_step, ralston2_step, heun3_step, ssprk3_step, and ralston3_step.

These changes aim to improve the maintainability and readability of the codebase while adding new functionality to the dendritex module.