fix(color): "gracefully" handles filechoice UI when too much file are present

[3djc]

This fixes #7343

The heart of the issue is that the table holding the value exceeds the maximum coordinates accepted by LVGL in our current configuration.

This PR computes the number acceptable in a given hardware (screen resolution and layout does matter here).

If the number of files in a give choice exceed the limit, a too much file message is shown instead, and actual file number vs limits is also displayed in second line.

The alternative would be to move to LV_USE_LARGE_COORD accepting 32 bits coordinates, but the ripple effects of that would need to be understood.

NOT tested since I don't have a large enough sound list :D

[philmoz]

Using LV_USE_LARGE_COORD would be better since it eliminates the problem altogether.
The 'coord_t' type used in the firmware code is already an int (32 bits)

Tested on TX16S Mk2 and it works without any obvious issues.
Tested with > 1200 entries in the file choice popup menu.

One code change is required (in addition to setting LV_USE_LARGE_COORD to 1)
src/gui/colorlcd/libui/keyboard_base.cpp line 187

      setTop(max((coord_t)coords.y2 + 21, LCD_H - height()));

[3djc]

Alternative is in #7358.

[pfeerick]

Closing as #7358 fixes the underlying issue, and the rest is education / documentation related.