Fix: Generate category hotkeys on init

[emyxiv]

Move the code responsible of generating category related purposes away from Input.PurposesWithCategories. The variables PurposesCategories, PurposesCategoriesHold and PurposesCategoriesToggle are not populated on init.

This fixes the issue where category-based hotkeys would not work until config input tab is displayed.

Thanks to Quickdraw6 for reporting this issue.