pf tests: test setting and retrieving timeout values

vnet tests: check for if_bridge.ko

A number of tests create a bridge, but did not check if if_bridge.ko is loaded.

We usually get away with that, because `ifconfig bridge create` autoloads the
module, but if we run the tests in a jail (e.g. because of kyua's upcoming
execenv.jail.params feature) we can't load the module and these tests can fail.

Check if the module is loaded, skip the test if it is not.

Reviewed by: markj
MFC after: 1 week
Event: Kitchener-Waterloo Hackathon 202406
Differential Revision: https://reviews.freebsd.org/D45487

pf tests: fix typos in the abort_v6 test case head / cleanup function name

MFC after: 1 week

Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

pf tests: test SCTP pfsync

Ensure that SCTP connections survive a failover to the backup pf
instance.

MFC after: 3 weeks
Sponsored by: Orange Business Services
Differential Revision: https://reviews.freebsd.org/D40869

pf tests: test 'rdr' for SCTP

Explicitly test that we cannot change the port number with rdr.
That's not a desireable feature on SCTP, because it could break
multihomed connections.

MFC after: 3 weeks
Sponsored by: Orange Business Services
Differential Revision: https://reviews.freebsd.org/D40868

pf tests: test SCTP NAT

MFC after: 3 weeks
Sponsored by: Orange Business Services
Differential Revision: https://reviews.freebsd.org/D40867

pf tests: test SCTP 'return'

Ensure that we send a correct abort message for 'block return' rules.

Test this by validating that nc doesn't sit around waiting for a
connection. It should give up immediately when it receives the abort.

MFC after: 3 weeks
Sponsored by: Orange Business Services
Differential Revision: https://reviews.freebsd.org/D40865

pf tests: basic SCTP connection test

pf can now inspect SCTP. Check that we can set up a connection.
IPv4 and IPv6 tests.

MFC after: 3 weeks
Sponsored by: Orange Business Services
Differential Revision: https://reviews.freebsd.org/D40863