Add script for getting info about recently registered users (#10290)

changelog.d/10290.feature

debian/changelog

debian/hash_password.1

debian/hash_password.ronn

debian/manpages

debian/matrix-synapse-py3.links

debian/register_new_matrix_user.1

debian/register_new_matrix_user.ronn

debian/synapse_port_db.1

debian/synapse_port_db.ronn

debian/synapse_review_recent_signups.1

debian/synapse_review_recent_signups.ronn

debian/synctl.1

debian/synctl.ronn

scripts/synapse_review_recent_signups

synapse/_scripts/review_recent_signups.py

synapse/storage/database.py