sdbus++: Use native types for obj-path and signature
sdbus++: Use native types for obj-path and signature

Change-Id: I6075a6a52553d0dc7dca6abc3442282f91fb5d44
Signed-off-by: Patrick Williams <cbb7353e6d953ef360baf960c122346276c6e320@stwcx.xyz>

openbmc/sdbusplus,openbmc/sdbusplus,openbmc/sdbusplus,openbmc/sdbusplus