DD extra configs for Split Keyboard

[dunk2k]

Description

Config migration for split_hand_matrix_grid*, split_hand_pin*, and split_haptic_enable.

    "split": {
        "split_pin": {
            "pin": "D3"
            "low_left": true
        }
    }

    "split": {
        "matrix_grid": {
            "pins": ["D3", "D2"]
            "low_right": true
        }
    }

    "split": {
        "haptic": true
    }

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Issues Fixed or Closed by This PR

• n/a

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[dunk2k]

Would folk be able to test these changes with keyboards that have the above migrated config.h setting(s)?

[sigprof]

See #18254 — as usual, split issues are complicated.

[dunk2k]

Closing as linked PR takes precedence