Merge branch '2023-07-14-expo-initial-config-editor'

To quote the author:
This series provides a means to edit board configuration in U-Boot in a
graphical manner. It supports multiple menu items and allows moving
between them and selecting items. The configuration is defined in a data
format so that code is not needed in most cases. This allows the board
configuration to be provided in the devicetree.

This is still at an early stage, since it only supports menus. Numeric
values are not supported. Most importantly it does not yet support
loading or saving the configuration selected by the user.

To try it out you can use something like:

    ./tools/expo.py -e test/boot/files/expo_layout.dts \
        -l test/boot/files/expo_layout.dts -o cedit.dtb
    ./u-boot -Tl -c "cedit load hostfs - cedit.dtb; cedit run"

Use the arrow keys to move between menus, enter to open a menu, escape
to exit.

Various minor fixes and improvements are provided in this series:
- Update STB TrueType library to latest
- Support clearing part of the video display
- Support multiple livetrees loaded at runtime
- Support loading and allocating a file
- Support proper measuring of text in expo
- Support simple themes for expo