Add block storage standalone service context

To support service level testing of the block storage service, a
standalone service context has been added that constructs a
service provider with backend storage for testing via the standard
service RPC interface.

Signed-off-by: Julian Hall <julian.hall@arm.com>
Change-Id: I866da635d0a6563cae9ed4de92f915107a5e3de5
6 files changed