mqtt: Improve frame parsing w/mult. PDUs

[jlucovsky]

Continuation of #10305

Issue: 6592

Link to redmine ticket: 6592

Describe changes:

• Parse PDU instead of entire stream

Updates:

• Update commit message per @catenacyber comment.

Provide values to any of the below to override the defaults.

To use a pull request use a branch name like pr/N where N is the
pull request number.

Alternatively, SV_BRANCH may also be a link to an
OISF/suricata-verify pull-request.

SV_REPO=
SV_BRANCH=pr/1609
SU_REPO=
SU_BRANCH=
LIBHTP_REPO=
LIBHTP_BRANCH=

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (244a35d) 73.31% compared to head (f55627f) 82.34%.

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #10309       +/-   ##
===========================================
+ Coverage   73.31%   82.34%    +9.02%     
===========================================
  Files         895      978       +83     
  Lines      148215   272029   +123814     
===========================================
+ Hits       108666   224001   +115335     
- Misses      39549    48028     +8479     

Flag	Coverage Δ
fuzzcorpus	63.59% <100.00%> (+0.11%)	⬆️
suricata-verify	61.50% <100.00%> (-0.03%)	⬇️
unittests	62.84% <0.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

[suricata-qa]

WARNING:

ERROR: QA failed on SURI_TLPR1_alerts_cmp.

field	baseline	test	%
	SURI_TLPW1_stats_chk
.flow.spare	999831	1100135	110.03%
	SURI_TLPR1_stats_chk
.memcap_pressure	57	46	80.7%
.memcap_pressure_max	62	70	112.9%
.http.memuse	373800	437344	117.0%

Pipeline 18068

[catenacyber]

Looks good to me

[victorjulien]

Merged in #10419, thanks!