Preparation for SdlInstance usage removal in RNIB

Preparation for SdlInstance usage removal in RNIB

SdlInstance type with its API functions has been deprecated and its
source code will be removed at some point of time from SDLGO repository.
SDLGO repository provides the SyncStorage type what should be used
instead of the SdlInstance type.

Since there exists applications that are using RNIB, it's not possible
just to replace SdlInstance with SyncStorage in RNIB code but instead
this commit is a first step where it's implemented a new RNIB interface
that utilizes SDL SyncStorage and it is left the existing RNIB interface
still in place. After some reasonable time has passed there will be made
next RNIB commit to remove the old RNIB code based on use of the SDL
SdlInstance type.

This commit has following changes:
* Implement a new ISdlSyncStorage interface type.
* Implement a new function GetNewRNibReader to create RNIB reader
  instance.
* Add deprecation warning for GetRNibReader function. All application
  should use instead GetNewRNibReader to create RNIB reader instance.
* Change RNIB reader instance APIs to use either SDL SdlInstance or
  SyncStorage instance depending on was the RNIB instance created by
  GetNewRNibReader or GetRNibReader function.
* Add unit tests to cover both the SdlInstance and the SyncStorage SDL
  APIs use cases.
* Add deprecation warnings to those RNIB code blocks and test cases that
  will be removed later when it's time to remove SDL SdlInstance from
  the code repository.

Issue-Id: RIC-805

Signed-off-by: Timo Tietavainen <timo.tietavainen@nokia.com>
Change-Id: I68345de5664edb4245f18f550a40974a4f79ad92