feat: Rich tables for MSWord backend (#2291)

* Adding support of rich table cells to MSWord backend

Signed-off-by: Maksym Lysak <mly@zurich.ibm.com>

* Fixes for properly accounting lists, pictures and headers in rich table cells

Signed-off-by: Maksym Lysak <mly@zurich.ibm.com>

* Cleaned up msword backend, re-generated docx tests

Signed-off-by: Maksym Lysak <mly@zurich.ibm.com>

* Added detection of simple table cells in word backend

Signed-off-by: Maksym Lysak <mly@zurich.ibm.com>

* Cleaned up

Signed-off-by: Maksym Lysak <mly@zurich.ibm.com>

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Signed-off-by: Maksym Lysak <mly@zurich.ibm.com>
Co-authored-by: Maksym Lysak <mly@zurich.ibm.com>