Use SSBO loads instead.
Add a new `GlyphQuad` interface.
Note that this reduces the size of glyph batch since the
buffer is always fully uploaded.
Can be improved with partial update later on if that causes
significant performance regression.
The motivation for this is to remove the instance buffer from
the batch API.
Pull Request: https://projects.blender.org/blender/blender/pulls/145225
7becc38a3c