Handle vector-image-converted text in PDFs

### Requested feature

Our users encounter from time to time documents that instead of text have vector path's representing themselves as text.
Because of the vector nature of it, we do not automatically OCR such pages, and because there is no actual text in such PDF pages, conversion output is usually empty.

### Alternatives

As a solution we need to reliably detect such cases, and render such pages into raster images, then running them through standard OCR pipeline. We can use layout model output to detect such cases, if layout model predicts text blocks that don't have programmatic text associated with them, this could be a good indication.