app-layer/template: use a max number of txs

[catenacyber]

Link to redmine ticket:
https://redmine.openinfosecfoundation.org/issues/6773

Describe changes:

• app-layer/template: use a max number of txs

As is done for every used protocol

[codecov]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (9fe00ff) 82.52% compared to head (a50186e) 82.52%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #10367      +/-   ##
==========================================
- Coverage   82.52%   82.52%   -0.01%     
==========================================
  Files         978      978              
  Lines      272148   272157       +9     
==========================================
- Hits       224595   224591       -4     
- Misses      47553    47566      +13     

Flag	Coverage Δ
fuzzcorpus	63.59% <44.44%> (-0.01%)	⬇️
suricata-verify	61.88% <33.33%> (-0.01%)	⬇️
unittests	62.83% <22.22%> (-0.01%)	⬇️

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[victorjulien]

Merged in #10413, thanks!