pf: fix mem leaks upon vnet destroy

[igoro]

Summary

It adds missing cleanup actions:
- remove user defined anchor rulesets
- remove user defined ether anchor rulesets
- remove tables linked to user defined anchors
- deal with wildcard anchor peculiarities to get them removed correctly

PR:             274310

Test Plan

Tom's shell script reports whether such mem leaks are present or not. It's attached to 274310.

[kp]

sys/netpfil/pf/pf_ioctl.c

6247

Let's assert this.

6267

Let's assert that this succeeds.

[igoro]

• The assertions have been added.
• This update also proposes to apply the same assertion for the main two anchors (existing code).