modules: littlefs: move CMake glue code from littlefs repo into Zephyr

Fixes: #40559

Moving CMakeLists.txt gluecode into Zephyr repo minimizes the patching
needed in LittleFS repo.

It provides a dedicate Zephyr LFS config header which will define the
equivalent LittleFS settings based upon Kconfig settings.
This further reduces the patching needed in LittleFS.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>