Output alert applayer v19.1

[catenacyber]

Link to redmine tickets:
https://redmine.openinfosecfoundation.org/issues/3827
Preliminary work for https://redmine.openinfosecfoundation.org/issues/5053

Describe changes:

• output: unify boilerplate code (trying to become a lines-of-code neutral contributor to Suricata ;-) and rising the percentage of rust files )
• output/dns: do not add empty app-layer metadata
• dnp3: restrict function scope to one file

There is one behavior change for SSH switching from LOG_DIR_PACKET to LOG_DIR_FLOW
What do you think about it ?

#9870 rebased

SV_BRANCH=pr/1490

OISF/suricata-verify#1490

[suricata-qa]

Information: QA ran without warnings.

Pipeline 17517

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (1dcf69b) 82.19% compared to head (a992684) 82.10%.
Report is 10 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #10166      +/-   ##
==========================================
- Coverage   82.19%   82.10%   -0.09%     
==========================================
  Files         974      962      -12     
  Lines      271825   271435     -390     
==========================================
- Hits       223416   222855     -561     
- Misses      48409    48580     +171     

Flag	Coverage Δ
fuzzcorpus	62.77% <79.52%> (-0.25%)	⬇️
suricata-verify	61.35% <98.42%> (-0.06%)	⬇️
unittests	62.92% <37.79%> (+0.08%)	⬆️

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[catenacyber]

Replaced by #10300