For nr_DRB_preconfiguration() and fill_default_secondaryCellGroup(),
there is duplicated code to generate and RLC-BearerConfig, when calling
the existing get_DRB_RLC_BearerConfig() (with the right parameters)
yields a similar configuration (see exceptions below).

Differences:
- We do not support reestablishmentRLC, so we don't set it
- Set prioritisedBitrate to 8kbps instead of infinity (we don't
  prioritize anything, anyway)
- bucketSizeDuration is 50ms instead of 100ms