Decouple filepaths from rcS/MTD using Kconfig

[PetervdPerk-NXP]

As an alternative to #20805 and discussed in today's dev call.

File path configuration through Kconfig.

For now we only introduce symbols for param and logger.

• BOARD_LOG_DIR
• BOARD_PARAM_FILE

Furthermore we generate a ROMFS rc.filepaths that takes BOARD_PARAM_FILE

[PetervdPerk-NXP]

@dagar I've changed the mechanism a bit could you take a look it?

@Igor-Misic I've added a second commit here as well to use LittleFS on the fmu-v6xrt. I saw you were working on LittleFS before would you be able to test this on your hardware and share your thoughts?

[PetervdPerk-NXP]

Moved the LittleFS commit to #22749
Overall I think it's ready for review.
Also this PR poses a potential fix for #22590 because one simply has to format the QSPI with a filesystem and then define BOARD_LOG_DIR to point to the mount point of the filesystem.

[davids5]

@PetervdPerk-NXP I am looking at the notion of replacing the persistent storage location /fs/microsd across the system. This path is hardcoded in a lot of places, UAVCAN, NetMan, DataMan etc. The approach I was considering was to create #if !defined(PX4_ROOT_STOAGE) and set it in board_comon.h to the current default.. Then any board can override it by setting it in board_config.h. Now that you have this mechanism; What would you suggest should be done?

[PetervdPerk-NXP]

Superseded by #23003