Support SlicingConfig for 5G Slicing Configuration

- add new HAL APIs getSlicingConfig() and getSlicingConfigResponse()
- create structs SlicingConfig, UrspRule, RouteSelectionDescriptor,
  RouteSelectionDescriptorParams, Nssais, and RejectedSliceInfo
- add SliceRejectionCause

Bug: 178075054
Test: run "atest VtsHalRadioV1_6TargetTest" and check the result for
      getSlicingConfig is PASSED
[3/13] PerInstance/RadioHidlTest_v1_6#getSlicingConfig/0_slot1: PASSED (15ms)

Change-Id: I5dc97d3c49d0bf4726975a5558360ebf9c09224b