Add back default Encoder Callbacks for Keychron Q/V series

[adophoxia]

Description

After #18713, the default encoder callbacks for the encoder variants of the Q2 were removed, and every Q and V board after that followed suit, which became problematic for users of QMK Configurator where after flashing the firmware from there, even with the encoder press working properly (KC_MUTE), rotation actions never work since as before, the callbacks were removed.

This PR is to add them back to rectify this issue to where even in the QMK Docs:

Those who are adding new keyboard support where encoders are enabled at the keyboard level should include basic encoder functionality at the keyboard level (<keyboard>.c) using the encoder_update_kb() function, that way it works for QMK Configuator users and exists in general.

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

• Update Q1 and Q2 for keychron #18713

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).

[adophoxia]

After some discussion with @drashna over in the QMK Discord, decided to move all of the encoder callbacks into the main <kb.c> file for each board instead of inside the <keyboard_variant.c> file to reduce boilerplate.

[vinorodrigues]

With #20320 merged, is this even relevant? Literally does the same thing as the new quantum/encoder.c L79-L103

[adophoxia]

After come careful consideration, I'm closing this PR due to the existence of #20320.