meta filter: allow to match on multiple fields at once

[vlrpl]

The goal here is to have "&&" or "and" support only.

-m "sk_buff.dev.name == 'eth0' && sk_buff.mark == 0xf00"

[vlrpl]

this probably pairs better with something proposed by @atenart and may end up becoming a new feature request.
If the above results to be ok, we might want to consider having a more complex dsl (maybe with both and/or and parentheses) using something like pest + a simple AST + ...