Add options for enabling DNS based cilium network policies

[mcolmant]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespaces from that line:

/kind api-change /kind bug /kind cleanup /kind design /kind documentation /kind failing-test /kind feature /kind flake

What this PR does / why we need it: It adds 2 variables for enabling the use of DNS based Cilium network policies and for configuring the DNS cache TTL.

Which issue(s) this PR fixes:

Fixes #11047

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

add cilium_enable_l7_proxy and cilium_tofqdns_min_ttl variables