suricata: move SuricataMain into main()

suricata: move SuricataMain into main()

Move the contents of SuricataMain into the `main()` function found in
main.c. This forces the Suricata application to bootstrap and run
Suricata through the same interfaces as a library user might do.

Required exposing StartInternalRunMode as SCStartInternalRunmode. Its
arguable whether those "actions" belong in the library or just the
application, but I think that is separation we can look at later.

For now the lib example and Suricata's own main are the same, however
the example will probably extend more into programmatically
configuring Suricata or dynamically registering a runmode, which
doesn't really belong the main Suricata application.