BUG/MEDIUM: http_ana: handle yield for "stats http-request" evaluation

BUG/MEDIUM: http_ana: handle yield for "stats http-request" evaluation

stats http-request rules evaluation is handled separately in
http_process_req_common(). Because of that, if a rule requires yielding,
the evaluation is interrupted as (F)YIELD verdict return values are not
handled there.

Since 3.2 with the introduction of costly ruleset interruption in
0846638 ("MEDIUM: stream: interrupt costly rulesets after too many
evaluations"), the issue started being more visible because stats
http-request rules would be interrupted when the evaluation counters
reached tune.max-rules-at-once, but the evaluation would never be
resumed, and the request would continue to be handled as if the
evaluation was complete. Note however that the issue already existed
in the past for actions that could return ACT_RET_YIELD such as
"pause" for instance.

This issue was reported by GH user @Wahnes in #3087, thanks to him for
providing useful repro and details.

To fix the issue, we merge rule vedict handling in
http_process_req_common() so that "stats http-request" evaluation benefits
from all return values already supported for the current ruleset.

It should be backported in 3.2 with 0846638 ("MEDIUM: stream: interrupt
costly rulesets after too many evaluations"), and probably even further
(all stable versions) if the patch adaptation is not to complex (before
HTTP_RULE_RES_FYIELD was introduced) because it is still relevant.