Implement two phase commit

When leadership is lost while applying a WalFrames command with commit=1, the Methods object has no way to tell if the log entry actually got committed or not. We should investigate implementing an additional command for two-phase commit, so we can be sure that the commit went through or not. See the TestIntegration_MethodHookLeadershipLost#wal frames sub-test.

Start by reading the TestIntegration_MethodHookLeadershipLost#wal frames sub-test and trace the WalFrames command behavior when leadership is lost with commit=1. Define the two-phase commit command and verify that the Methods object can determine whether the log entry committed or not.

Written by the indexing model from the issue text.