Fix 'qmk new-keyboard' processing of development_board

[zvecr]

Description

Config would be created without the "board" config, which for blackpills fails to configure its HSE frequency correctly.

Instead of expanding development_board to its relevant config , just use the setting directly.

Also fixes the case of qmk import-keyboard where the json file is using development_board. Previously it would have processor/bootloader keys with unresolved tokens.

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

• https://discord.com/channels/440868230475677696/867530222407778344/1255208257463517205

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).