http: implement min size stream logic

http: implement min size stream logic

Update HTTP parser to set the min inspect depth per transaction. This
allows for signatures to have their fast_pattern in the HTTP body,
while still being able to inspect the raw stream reliably with it.

The inspect depth is set per transaction as it:
- depends on the per personality config for min inspect size
- is set to the size of the actual body if it is smaller

After the initial inspection is done, it is set to 0 which disables
the feature for the rest of the transaction.

This removes the rescanning flush logic in commit
7e004f52c60c5e4d7cd8f5ed09491291d18f42d2 and provides an alternative
fix for bug #2522. The old approach caused too much rescanning of
HTTP body data leading to a performance degradation.

Bug #2522