Removed SR store implementation detail from wsrep-lib

The following was moved to application side implementation:

- Removed sr_store from streaming context.
- Removed sr_state from transaction.
- Removed get_binlog_cache() from client_service interface.

Other:
- Add SR applier reference to append_fragment_and_commit() to
  make it available for application.
- Add separate interface call to rollback SR transactions
  on disconnect. Rolling back SR transactions due to rollback
  fragment and rolling back SR transactions due to disconnect have
  different behaviors. Have separate calls for these different
  cases for clarity.
- Remove non-const transaction accessor, not needed anymore because
  SR state has been moved to application side.
- Remove unneeded set_fragments_from_table().

dbsim/db_client_service.hpp

@@ -90,11 +90,6 @@ namespace db
         void debug_sync(const char*) override { }
         void debug_crash(const char*) override { }
 
-        void *get_binlog_cache() override
-        {
-            return (NULL);
-        }
-
         int fragment_cache_remove_transaction(
             const wsrep::id&,
             wsrep::transaction_id) override