[android] Make pixel size fonts work properly

This reverts commit ac4ae78d because it breaks the font sizing when disabling UI scaling. Instead it now properly handles all places that want to change a font's relative size by checking whether the font was in pixels or points.

Places that just set the font to a fixed point size aren't a problem, so they've been left untouched.

BUG:515585

Test Plan

• Observe that places with relative font sizes work on Android, e.g. the welcome page has slightly larger fonts for the text at the bottom.
• On an Android device with natural UI scaling, disable the scaling by unchecking Settings → Configure Krita → General → Window → Enable HiDPI support.
• Restart Krita.
• Observe that the font has the proper size instead of being really huge.

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.
• Does the patch add a user-visible feature? If yes, is there a documentation MR ready for it at Krita Documentation Repository?

Reminder: the reviewer is responsible for merging the patch, this is to ensure at the least two people can build the patch. In case a patch breaks the build, both the author and the reviewer should be contacted to fix the build. If this is not possible, the commits shall be reverted, and a notification with the reasoning and any relevant logs shall be sent to the mailing list, kimageshop@kde.org.