Because

1) those services are needed and used only by ru/ promises like check_cpri_lock
   and check_rx_saturated.
2) in general we will need to initialize and setup radio units not only in eNB -
   for example UEsim will use the same code library to initialize radio units.
   Thus the proper place to keep everything required for RU to be operational have to
   be located inside ru/ and activated by that radio-units library.

Push corresponding code from instance-enb to ru/ and do only minor adjustments
to instance-gnb trying not to break it, since gnb does not currently use rulib,
and because in the future gnb will be replaced by enb which will be serving
both lte and nr cells in the same service.

/cc @lu.xu, @tomo, @xavier_thompson, @Daetalus
/reviewed-by @jhuge
/reviewed-on !1511