Implement killSessions command

[b1ron]

What should be done?

• https://www.mongodb.com/docs/manual/reference/command/killSessions/#mongodb-dbcommand-dbcmd.killSessions

Use cases to consider

Please note! For testing, authentication must be enforced (e.g. through --auth flag in MongoDB), so different users have different uids for sessions, and therefore testing is more accurate.

This is not the full list of use cases, but list of scenarios that comes to the mind:

• Call killSessions for a non-existent session
• Call killSessions for a session of another user (not the currently authenticated user)
• Call killSessions for an existing session of the current user and try to call killSessions / refreshSessions / endSessions for the same session again.
• Attempt to use lsid of the killed session for a new operation.
• Call find, getMore, kill the current session, test what happens with the cursor (it will be closed)
• Attempt to call killSessions for all possible states of a transaction
  • Move this item to transaction implementation task if irrelevant for now
• Think of other test cases with "in progress" operations (if possible) - killing a session should kill such operations
  • Can this be implemented by attaching a context to each session, using this context for command execution, and closing this context if a session is killed?..