fix: ensure correct callback behavior with reusable states

[definitelyokay]

Reworks LogicBlocks to ensure OnEnter/OnExit is called in the correct order for states that are reused.

• Adds support for multiple initial state types to the diagram generator
• Adds support for partial states spread across files to the diagram generator.
• Simplifies the LogicBlock core state change mechanism.
• Adds internal state to StateLogic so callbacks can be preserved inside the state rather than inside the logic block. This is the mechanism which enables the fix above.
• Updates all API usage, fixes tests, and introduces new tests for desired use cases.