detect-state: handle duplicate inspect/match

detect-state: handle duplicate inspect/match

If for a packet we have a TX N that has detect state and a TX N+1 that
has no detect state, but does have 'progress', we have a corner case
in stateful detection.

ContinueDetection inspects TX N, but cannot flag the rule in the
de_state_sig_array as the next (TX N+1) has already started and needs
to be inspected. 'StartDetection' however, is then unaware of the fact
that ContinueDetection already inspected the rule. It uses the per
session 'inspect_id' that is only moved forward at the end of the
detection run.

This patch adds a workaround. It uses the DetectEngineThreadCtx::
de_state_sig_array to store an offset between the 'base' inspect_id
and the inspect_id that StartDetection should use. The data type is
limited, so if the offset would be too big, a search based fall back
is implemented as well.