Add the following metrics to server status:

• repl.stepDown.userWriteOperationsKilled: Write operations killed by stepdown.
• repl.stepDown.userReadOperationsRunning: Read operations left running at stepdown
• repl.network.secondaryLegacyUnacknowledgedWrites: Write operations to a secondary which resulted in a disconnection due to being an unacknowledged write (legacy ops)
• repl.network.secondaryUnacknowledgedWrites: Write operations to a secondary which resulted in a disconnection due to being an unacknowledged write

Add the following logging:

• At stepdown log the number of operations killed and preserved.
• Log when an unacknowledged write results in a disconnection.