Replace td_fn_rctrl with generic td_layer_mod

Replace td_lshift_fn with generic td_mod_layer, add TD_RCTL_FN

Move TD_FN_RCTL after TD_RCTL_FN

Update tap dance function names

Set preferred intervals for rgblight effects

Add GODSPEED_YELLOW color

Update GODSPEED_BLUE values and RGB mode keys

Set Melody96 underglow color to Godspeed blue on EEPROM reset

Remove most _keymap and _user definitions in userspace

Some keyboards misuse _user functions by defining them in the base files
instead of the corresponding _kb functions (especially led_set_user and
matrix_init_user). Until this is fixed (#5148), I've removed definitions
in my userspace that could cause linking collisions.

Make toggle_numpad a nested function in process_record_user

Add _keymap versions of other custom Quantum functions

Not added: eeconfig_update_keymap, eeconfig_read_keymap

Use two spaces before inline comments

Switch to UNICODEMAP in keyboard rules

Avoid collisions with X_* send string constants

Generate UNICODE and UNICODEMAP constants using macros

Add RGB_SET keycode to Melody96 and RGB files to userspace

Add RGB controls and numpad Unicode to Melody96 keymap

Use "Vo-", "Vo+" instead of "VoD", "VoU" in keymap comments

Move feature flags from userspace into keyboard rules

Add melody96:konstantin keymap

Update custom SEND_STRING