tests/netgraph: Tests for ng_vlan_rotate

Test functionality of ng_vlan_rotate(4):
- Rotate 1 to 9 stagged vlans in any possible direction and length
- Rotate random combinations of ethertypes (8100, 88a8, 9100)
- Automatic reverse rotating for backward data flow
- Test too many and too few vlans

Reviewed by: kp (earlier version)
Differential Revision: https://reviews.freebsd.org/D30670

(cherry picked from commit 6b08e68be111d50931b0d30145f8b7e3402decaf)

Git Hash: 7438333663b4d22f6863aeffba55d6a04149e3a2
Git Author: donner@FreeBSD.org

tests/netgraph: Tests for ng_hub

Test functionality of ng_hub(4):
- replicting traffic to anything but the sending hook
- persistence
- an unrestricted loop
- implementation limits with many hooks.

Reviewed by: kp
Differential Revision: https://reviews.freebsd.org/D30633

(cherry picked from commit 7863faa78ae271017c404c635b2a9d07379d4316)

Git Hash: d68f32b4ac357ebd54dd1c640bb87ba92d7eb76d
Git Author: donner@FreeBSD.org

tests/netgraph: Tests for ng_bridge

Test functionality of ng_bridge(4):
- replicating traffic to anything but the sending hook
- persistence
- detect loops
- unicast to only one link of many
- stretch to implementation limits on broadcast

Reviewed by: kp
Differential Revision: https://reviews.freebsd.org/D30647
Differential Revision: https://reviews.freebsd.org/D30699

(cherry picked from commit 61814702398ce29430b2bef75cbdd6fd2c07ad12)
(cherry picked from commit 5554abd9cc9702af30af90925b33c5efff4e7d88)

Git Hash: 49736a31a5c29319c6dc8f9080b3a85da2305b47
Git Author: donner@FreeBSD.org

tests/netgraph: Inital framework for testing libnetgraph

Provide a framework of functions to test various netgraph modules.
Tests contain:
- creating, renaming, and destroying nodes
- connecting and removing hooks
- sending and receiving data
- sending ASCII messages and receiving binary responses
- errors can be passed for indiviual inspection or fail the test

Reviewed by: kp
Differential Revision: https://reviews.freebsd.org/D30629
Differential Revision: https://reviews.freebsd.org/D30657
Differential Revision: https://reviews.freebsd.org/D30671
Differential Revision: https://reviews.freebsd.org/D30699

(cherry picked from commit 24ea1dbf257aa6757f469bcd859f90e9ad851e59)
(cherry picked from commit 09307dbfb888a98232096c751a96ecb3344aa77c)
(cherry picked from commit 9021c46603bf29b9700f24b8dce8796b434d7c8f)
(cherry picked from commit 5554abd9cc9702af30af90925b33c5efff4e7d88)

Also contains some fixups:
- indent all files correctly
- finish factoring out
- remove debugging code
- check for renaming issues reported in PR241954

PR: 241954
Differential Revision: https://reviews.freebsd.org/D30692
Differential Revision: https://reviews.freebsd.org/D30714
Differential Revision: https://reviews.freebsd.org/D30713

(cherry picked from commit a664ade93972ce617f0888ff79e715dff9cf0f87)
(cherry picked from commit 0afa9be03937d60cb5aeba64c81e3e2165bd3737)
(cherry picked from commit 43e4821315c31db067e23564b9bfafb519e77b2b)

Git Hash: 4a0c1d0543afd83156b50b3f9b74c79e74cf526f
Git Author: donner@FreeBSD.org

tests/netgraph: Prebuild tests directory

(partially cherry picked from commit e8db04c38959c882fe17e7c2b26fbabe74f26311)

Git Hash: abeb0d0c29ba28f3f502931adfa8d98758ff116e
Git Author: donner@FreeBSD.org