[Core] Fix flipped logic bug with One Shot OS_ON / OS_OFF keys

[getreuer]

The One Shot documentation says key OS_ON turns one-shot keys on and OS_OFF turns them off. The actual behavior is flipped: OS_ON turns them off and OS_OFF turns them on. This PR fixes this.

Description

This bug was discovered by reddit user u/Dutchnesss1. I can reproduce it on my keyboards. We were troubleshooting a problem where one-shot keys weren't work on Dutchnesss1's keyboard, and confusingly, OS_ON disabled one-shot keys when we thought we were enabling them.

The underlying problem is the logic for functions oneshot_set(), oneshot_enable(), oneshot_disabled(), and is_oneshot_enabled() are similarly flipped. The bug is rather obvious once looking at their implementation (code link):

void oneshot_set(bool active) {
    if (keymap_config.oneshot_disable != active) {
        keymap_config.oneshot_disable = active;
        eeconfig_update_keymap(keymap_config.raw);
        clear_oneshot_layer_state(ONESHOT_OTHER_KEY_PRESSED);
        dprintf("Oneshot: active: %d\n", active);
    }
}

void oneshot_enable(void) {
    oneshot_set(true);
}

Calling oneshot_enable() calls oneshot_set(true), which sets keymap_config.oneshot_disable = true.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

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).