Add glyph palette

This adds a QML driven glyph palette to the text tool. It can do 2 things: firstly, it can show a character map of the given font, secondly, it can present both glyph alternates and variation selectors. While there will be toggles for opentype features as well, a glyph palette can be the most intuitive way to select these.

text-tool-demo-feb-glyph-palette-2024-02-26_12.19.38.mp4

TODO:

• Use unicode blocks instead of scripts for filtering, this will require generating a blocks file from UCD text file.
• Allow filtering by string.
• Make glyph alts pop-up a qtwidgets popup, because QtQuickWidget clips QML pop-ups.
• Improve tooltips/localize
• Improve harfbuzz glyph retrieval code (localize).
• Docs

Test Plan

Test the glyph palette by editing a text with a font that uses opentype features:

1. The demo uses MonteCarlo from google fonts, another good test font is Junicode, which has tons of alternate glyphs, but even Noto Sans has small caps.
2. For variation selectors, you can try Source Han or Noto Sans CJK, 邉󠄀 (edge) is the character with the most variation selectors.

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.

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