DOC: lua: prefer Patref:{set,add}() over legacy methods for acl and maps

DOC: lua: prefer Patref:{set,add}() over legacy methods for acl and maps

Patref:set() can achieve the same thing as core.set_map()
Patref:add() can achieve the same thing as core.add_acl()
Patref:del() can achieve the same thing as core.del_map() and
core.del_acl()

As a bonus, Patref:{set,add} are more efficient than their core
legacy equivalent, because they don't require systematic pattern
reference lookup for each individual operation.

Let's mention that in the doc to encourage Patref methods adoption.