Fix API review issues for 5G Slicing feature

- Rename SlicingConfig and SlicingException to
  NetworkSlicingConfig and NetworkSlicingException
- Rename SlicingError to NetworkSlicingError
- add subclasses for NetworkSlicingException and remove getErrorCode()
- make isRadioInterfaceCapabilitySupported() public

Bug: 183714964
Bug: 183937956
Test: full build pass
    - make -j200 doc-comment-check-docs
    - atest TelephonyManagerTest#testGetNetworkSlicingConfiguration
    - atest RadioConfigResponseTest
Change-Id: I4326b230c09adcf732f4271f3044d69c1ae5958c