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>

test/id_test.cpp

@@ -37,6 +37,15 @@ BOOST_AUTO_TEST_CASE(id_test_uuid)
 }
 
 BOOST_AUTO_TEST_CASE(id_test_string)
+{
+    std::string id_str("node1");
+    wsrep::id id(id_str);
+    std::ostringstream os;
+    os << id;
+    BOOST_REQUIRE(id_str == os.str());
+}
+
+BOOST_AUTO_TEST_CASE(id_test_string_max)
 {
     std::string id_str("1234567890123456");
     wsrep::id id(id_str);