Add gtk4's list models

These are part of gtk4 so we must have an in-tree copy to use them with gtk3.

File                  Commit
gtkfilterlistmodel.c  d3c45cb9796516aa2148daff816cee46efefa9fc
gtkfilterlistmodel.h  29c700d1c73094715ec510f8677934f27952fcc3
gtkrbtree.c           af56f06b7b6c1eb3f0aaeb567b79be9182b53555
gtkrbtreeprivate.h    8a7706f2b5cfc1dd7cdf0b8865fc05da0f4a6891
gtksortlistmodel.c    d3c45cb9796516aa2148daff816cee46efefa9fc
gtksortlistmodel.h    f3834138f7e8e8a3ef9945832876b4e5b4d1b719

Note: Some files are patched to build without gtk's private i18n headers

Obsoletes !271 (closed)