detect/iprep: implement isset and isnotset

detect/iprep: implement isset and isnotset

Implement special "isset" and "isnotset" modes.

"isset" matches if an IP address is part of an iprep category with any
value.

It is internally implemented as ">=,0", which should always be true if
there is a value to evaluate, as valid reputation values are 0-127.

"isnotset" matches if an IP address is not part of an iprep category.

Internally it is implemented outside the uint support.

Ticket: #6857.