src/context: support resolving PARTUUID to real path
src/context: support resolving PARTUUID to real path

The kernel command line 'root' option allows to pass partitions via
PARTUUID=xxx instead of passing the real device path.

Despite preferring explicit information about selected partition (i.e.
slot) provided by the bootloader (e.g. via slot.rauc argument) we should
also support resolving PARTUUID to the corresponding real device path.

Signed-off-by: Enrico Jorns <a2e5f936c390f36494e46e71bcfbe365bb1e8c49@pengutronix.de>

ejoerns/rauc,rauc/rauc,jluebbe/rauc,ejoerns/rauc,rauc/rauc,rauc/rauc,jluebbe/rauc,jluebbe/rauc,ejoerns/rauc