MINOR: sample: implement the T* timer tags from the log-format as fetches

MINOR: sample: implement the T* timer tags from the log-format as fetches

This commit implements the following timer tags available in the log
format as sample fetches:

	req.timer.idle (%Ti)
	req.timer.tq (%Tq)
	req.timer.hdr (%TR)
	req.timer.queue (%Tw)

	res.timer.hdr (%Tr)
	res.timer.user (%Tu)

	txn.timer.total (%Ta)
	txn.timer.data (%Td)

	bc.timer.connect (%Tc)
	fc.timer.handshake (%Th)
	fc.timer.total (%Tt)