Debug CLI to magically create / delete a TCP session

Debug CLI to magically create / delete a TCP session

The session ends up in established state, and is hand-crafted to look
like it was created by the builtin_server.

This will come in handy for injecting packets into tcp46-established,
along with ancillary debug CLI to adjust connection parameters.

Immediate applications include screwball window cases, out of order
segments, paws checking, and so on and so forth.

Debug CLI script:

loop create
set int ip address loop0 6.0.1.1/8
set int state loop0 up
set ip arp loop0 6.0.1.2 feed.face.babe
test tcp server
test tcp session

packet-generator new {
  name tcp
  limit 1
  node ip4-input
  size 100-100
  interface loop0
  no-recycle
  data {
    TCP: 6.0.1.2 -> 6.0.1.1
    TCP: 11234 -> 1234
    ACK window 2000
    seqnum 0
    acknum 0
    incrementing 100
  }
}

Change-Id: I866c2159376064b7d14f70531022c1fe949258c2
Signed-off-by: Dave Barach <dave@barachs.net>