Prevent additional taskbar entry when invoking the on-canvas color selector

This patch bypasses WM hints for the color selector popup in order to avoid extra taskbar entries. It also handles window activation events to avoid issues that comes with bypassing WM hints. See Qt::BypassWindowManagerHint and Qt::X11BypassWindowManagerHint at https://doc.qt.io/qt-5/qt.html#WindowType-enum

Test Plan

1. Create a new document
2. Trigger the on-canvas color selector popup (shift+I)
3. Observe that the on-canvas color selector popup no longer triggers a separate taskbar entry in KDE/Plasma environments

Please note if you run into input/WM issues related to the color selector or its popup. Especially on platforms other than KDE/Plasma.

Formalities Checklist

• I confirmed this builds.
• I confirmed Krita ran and the relevant functions work.
• I tested the relevant unit tests and can confirm they are not broken. (If not possible, don't hesitate to ask for help!)
• I made sure my commits build individually and have good descriptions as per KDE guidelines.
• I made sure my code conforms to the standards set in the HACKING file.
• I can confirm the code is licensed and attributed appropriately, and that unattributed code is mine, as per KDE Licensing Policy.