In preparation of more dynamic logic in rule loading also doing
some registration, allow for buffers to be registered as fast_patterns
during rule parsing.
Leaves the register time registrations mostly as-is, but copies the
resulting list into the DetectEngineCtx and works with that onwards.
This list can then be extended.
Move previously global table into detect engine ctx. Now that we
can register buffers at rule loading time we need to take concurrency
into account.
Move DetectBufferType to detect.h and update DetectBufferCtx API calls
to include a detect engine ctx reference.