When many text using BLF the glymp texture could be re-written.
In this case the new upload should be done in a separate render
graph node group. This wasn't the case and resulted in
validation warnings about the glyph texture being in an layout
that wasn't expected.
This PR simplifies the group extraction a bit by looking ahead
when the group ends.
Pull Request: https://projects.blender.org/blender/blender/pulls/123547
dbd04310c7