updates

[chaoming0625]

Description

• [running] fix multiprocessing bugs
• [math] add brainpy.math.gpu_memory_preallocation() for controlling GPU memory preallocation
• [math] clear_buffer_memory support to clear array and compilation both
• [dyn] compatible old version of .reset_state() function

How Has This Been Tested

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Documentation (non-breaking change which updates documentation)
• Breaking change (fix or feature that would cause existing functionality to change)
• Code style (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Other (please describe here):

Checklist

• [ ] Code follows the code style of this project.
• [ ] Changes follow the CONTRIBUTING guidelines.
• [ ] Update necessary documentation accordingly.
• [ ] Lint and tests pass locally with the changes.
• [ ] Check issues and pull requests first. You don't want to duplicate effort.

Other information