feat: Implement new reading-order model (#916)

* Implement new reading-order model, replacing DS GLM model (WIP)

Signed-off-by: Christoph Auer <cau@zurich.ibm.com>

* Update reading-order model branch

Signed-off-by: Christoph Auer <cau@zurich.ibm.com>

* Update lockfile [skip ci]

Signed-off-by: Christoph Auer <cau@zurich.ibm.com>

* Add captions, footnotes and merges [skip ci]

Signed-off-by: Christoph Auer <cau@zurich.ibm.com>

* Updates for reading-order implementation

Signed-off-by: Christoph Auer <cau@zurich.ibm.com>

* Updates for reading-order implementation

Signed-off-by: Christoph Auer <cau@zurich.ibm.com>

* Update tests and lockfile

Signed-off-by: Christoph Auer <cau@zurich.ibm.com>

* Fixes, update tests

Signed-off-by: Christoph Auer <cau@zurich.ibm.com>

* Add normalization, update tests again

Signed-off-by: Christoph Auer <cau@zurich.ibm.com>

* Update tests with code

Signed-off-by: Christoph Auer <cau@zurich.ibm.com>

* Push final lockfile

Signed-off-by: Christoph Auer <cau@zurich.ibm.com>

* sanitize text

Signed-off-by: Michele Dolfi <dol@zurich.ibm.com>

* Inlcude furniture, Update tests with furniture

Signed-off-by: Christoph Auer <cau@zurich.ibm.com>

* Fix content_layer assignment

Signed-off-by: Christoph Auer <cau@zurich.ibm.com>

* chore: Delete empty file docling/models/ds_glm_model.py

Signed-off-by: Nikos Livathinos <nli@zurich.ibm.com>

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Signed-off-by: Christoph Auer <cau@zurich.ibm.com>
Signed-off-by: Michele Dolfi <dol@zurich.ibm.com>
Signed-off-by: Nikos Livathinos <nli@zurich.ibm.com>
Co-authored-by: Michele Dolfi <dol@zurich.ibm.com>
Co-authored-by: Nikos Livathinos <nli@zurich.ibm.com>