detect/content-inspect: localize recursion counting

detect/content-inspect: localize recursion counting

Use stack local var instead of DetectEngineThreadCtx member. Instead
setup a stack local struct that both counts and holds the limit. Make sure
the limit is a const so we can avoid rereading it.

This is part of an effort to reduce the size of the DetectEngineThreadCtx
structure and reduce the number of memory writes to it. Additionally, it
is part of an effect to reduce the number of places where detection
tracks various forms of state.