[Bug] Add proper guarding via the FACTORY_TEST_ENABLE def to allow proper user space enhancements

[MarqueIV]

Describe the Bug

Add proper guarding via the FACTORY_TEST_ENABLE def to allow proper user space enhancements.

Note: I've already opened a PR with a fix for this issue, but it's just sitting there and has now been flagged with the 'stale' label. Please consider reviewing this.

PR: #441

Issue description:

In its current state, factory_test.c unconditionally defines dip_switch_update_user, preventing userspace configurations from overriding the Mac/Win DIP switch layer mapping. This goes against QMK coding practices as users are blocked from adding their own functionality.

Wrapping the existing code with #ifdef FACTORY_TEST_ENABLE allows users to #undef the define in their own keymap config.h and thus, they can provide their own implementation for this function, better following proper QMK code etiquette/style.

These changes also guard all factory_reset_indicating() calls across every board file (34 boards) which would fail to compile when FACTORY_TEST_ENABLE is undefined by a user, since factory_test.h includes are already conditionally guarded.

For default builds, these are no-op changes as FACTORY_TEST_ENABLE is currently always defined. This only affects user builds where users explicitly undef FACTORY_TEST_ENABLE to be able to properly define their own dip_switch_update_user call.

Keyboard Used

All Keychron QMK-based boards

Link to product page (if applicable)

n/a

Operating System

QMK

qmk doctor Output

n/a

Is AutoHotKey / Karabiner installed

• AutoHotKey (Windows)
• Karabiner (macOS)

Other keyboard-related software installed

n/a

Additional Context

Again, I've already opened a PR with this fix, but it's since gotten stale. Please consider reviewing it. Again, this is a no-op for your existing code, but allows people like me to heavily customize your firmware with your hardware. Thanks!

#441