The pattern template defines flows that have the same matching
fields but with different matching values.
For example, matching on 5 tuple TCP flow, the template will be
(eth(null) + IPv4(source + dest) + TCP(s_port + d_port) while
the values for each rule will be different.
Due to the pattern template can be used in different domains, the
items will only be cached in pattern template create stage, while
the template is bound to a dedicated table, the HW criteria will
be created and saved to the table. The pattern templates can be
used by multiple tables. But different tables create the same
criteria and will not share the matcher between each other in order
to have better performance.