cli: add user address matching helpers for notmuch reply

Add a multi-purpose address_match() function for matching strings
against user's configured primary and other email addresses. Add thin
wrappers user_address_in_string() and string_in_user_address() for
ease of use, and also convert existing address_is_users() to wrapper
for the same.

No functional changes.

Signed-off-by: Jani Nikula <jani@nikula.org>