Compression formats are limited to various sizes (16383×16383 for
WebP, 16384×16384 for Basis Universal). If the size is exceeded,
the texture fails to import. To avoid this, textures are now downsampled
with a warning printed when necessary.
The warning is not printed if the user has specified a size limit
and the size limit is being honored.
This also allows setting Size Limit up to 16383 pixels (the lowest
common denominator out of all compression modes), instead of being
limited to 4096 pixels.
Tooltips are displayed when hovering import options, both in the Import
dock and in the import defaults editor (which is in the Project Settings).
Co-authored-by: Rémi Verschelde <rverschelde@gmail.com>