Add support for custom provider implementation

- Add a set_provider_factory() method to server_state to allow
  injecting provider factory which will be called when the
  provider is loaded.

Other related changes:
- Implement to_string() helper method for id class.
- Fix id ostream operator human readable id printing.
- Pass victim client_service as an argument to provider::bf_abort()
  to allow passing victim context to custom provider.
- Implement prev() helper method for seqno class.
- Make server_state recover_streaming_appliers_if_not_recovered()
  public. In some recovery scenarios the method must be called outside
  of server_state internal code paths.
- Add storage_service requires_globals() method. The storage service
  implementation may override this to return false if changing to
  storage service context does not require store/reset globals.
- Change view final() to also require that the view status is not
  primary for the view to be final. Also change the method name to
  is_final() to avoid confusion with C++ final identifier.
- Fixes to server state handling in disconnecting and disconnected
  states.
- Keep TOI meta data over whole TOI critical section.

Co-authored-by: Denis Protivensky <denis.protivensky@galeracluster.com>

include/wsrep/client_state.hpp

@@ -582,7 +582,8 @@ namespace wsrep
          * @param lock Lock to protect client state.
          * @param bf_seqno Seqno of the BF aborter.
          */
-        int bf_abort(wsrep::unique_lock<wsrep::mutex>& lock, wsrep::seqno bf_seqno);
+        int bf_abort(wsrep::unique_lock<wsrep::mutex>& lock,
+                     wsrep::seqno bf_seqno);
         /**
          * Wrapper to bf_abort() call, grabs lock internally.
          */
@@ -593,7 +594,8 @@ namespace wsrep
          * should be called by the TOI operation which needs to
          * BF abort a transaction.
          */
-        int total_order_bf_abort(wsrep::unique_lock<wsrep::mutex>& lock, wsrep::seqno bf_seqno);
+        int total_order_bf_abort(wsrep::unique_lock<wsrep::mutex>& lock,
+                                 wsrep::seqno bf_seqno);
 
         /**
          * Wrapper to total_order_bf_abort(), grabs lock internally.