feat: Introduce modular docling-slim package (#3285)

* plans folder structure

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

* initial plan

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

* updated plan

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

* restructure repo for docling and docling-slim

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

* transpose package structures

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

* add all-packages

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

* updated  lock and deps

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

* align deps

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

* more lock like main

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

* more locked pinning

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

* rename extras

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

* add simple README for docling-slim

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

* fix scikit-image issue

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

* add readme placeholder

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

* add all extras in package test

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

* cli in docling-slim

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

* apply formatting

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

* fix testing package

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

* override grpcio in no-header test

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

* update lock

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

* update package description

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

* updated extras

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

* fix publish scripts

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

* update package test

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

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