Restructuring of some command subtrees

[maxlandon]

Note that this took me only an hour, it's just to illustrate something that I
think would be quite wise on the longer run. I also know this will break compatibility
with some users scripts/autoruns. I think it's worth doing this now, however, as
the window would be that wide open before long.

Discard if needed, didn't cost me much :)

Card

The present PR is a single-commit one aimed at moving some commands/subcommands
somewhere else in the tree, sometimes with a different verb.

Two objectives with this:

• More elegant command tree discovery, or more generic approach with some commands.
  (example: generate traffic-encoders becomes transports encoders in the server
  menu, which in turn enables to change reconfig to transports reconfig in the
  sliver implant menu.)

• Ensure a domain/activity-coherent tree of commands, so that any future development
  and new functionality can easily fit into it. This is mainly aimed at everything
  transports/C2 related, where one might see new dialers (bind) or staging stacks.

1) Changes (Server menu and excluding C2 stacks):

generate traffic-encoders   # becomes
tranports                   # Generic transport management.
        encoders

2) Changes (Sliver menu):

reconfig --jitter ...       # becomes
tranports                   # Our generic transport command has different uses for different contexts
        reconfig

msf --flags     # Both of these
msf-inject      # refactored into.

msf
    execute    # implementation of the former `msf` command
    inject     # 

Changes (C2 commands):

This last section is where most changes take place, since its whole purpose is to
enable forward development within a consistent/coherent tree.

# The `stage-listener` disappears, and is now reused in all protocol commands that support it.
http
    listen      # Classic Sliver listener: "stage" listener in Metasploit parlance.
    serve       # "Stager" listener in Msf parlance: We have content to serve (a stage).

https        # Same for https
    listen  
    serve

tcp          # The TCP protocol can only stage
    serve    # So here it is

mtls
    listen   # Contrarily to mTLS.

named-pipe
    listen

dns
    listen

# Same for Wireguard
wg-config   # both become
wg          
    config
    listen
    ...     # I didn't add portforwarders/socks however, would be a bit too much...

That enables to insert new stacks/tools like this:

mtls
    listen
    dial    # Someone writes a bind handler for mtLS

https
    listen
    dial    # Someone writes an HTTP server on the implant.
    serve
    send    # Someone writes a bind stager handler on the implant.

# In Sliver menu
tcp
    listen
    dial    # Bind handlers on pivots