[Core] Add a dynamic_macro_stop_recording(void) function.

[ariane-emory]

Description

This PR refactors the code used to stop recording a dynamic macro into it's own new function, void dynamic_macro_stop_recording(void), allowing users to programmatically end the recording of a dynamic macro.

An example of how this could be useful is that it would allow the user to, in their keymap, change the behavior of the QK_DYNAMIC_MACRO_PLAY_* keys to behave more like Emacs' key macros - where hitting the play 'key' while recording will stop recording and immediately play back the key macro, without requiring the user first perform a separate key stroke to explicitly end recording - by adding a case like this example to their process_record_user function:

  case QK_DYNAMIC_MACRO_PLAY_1:
  case QK_DYNAMIC_MACRO_PLAY_2:
    if (record->event.pressed)
      dynamic_macro_stop_recording();
    return true;

Other users may be able to imagine other situations where they'd like to programmattically end the recording of a dynamic macro (on a timer, perhaps, in case they start recording and then go AFK and forget to end the recording of their macro?).

On my local system, this change does not appear to change the size of the firmware produced.

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

None.

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).