rust: Convert to use Default/Self

[jlucovsky]

This PR updates the Rust source modules to use the more "modern" Self/Default constructs.

Link to redmine ticket: 4497

Describe changes:

• Modify to use Self/Default constructs within Rust source code modules

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[codecov]

Codecov Report

Merging #6136 (91a8a25) into master (533c6ff) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #6136      +/-   ##
==========================================
+ Coverage   76.87%   76.88%   +0.01%     
==========================================
  Files         613      613              
  Lines      186344   186344              
==========================================
+ Hits       143248   143270      +22     
+ Misses      43096    43074      -22     

Flag	Coverage Δ
fuzzcorpus	52.82% <ø> (+<0.01%)	⬆️
suricata-verify	50.97% <ø> (+0.01%)	⬆️
unittests	63.07% <ø> (ø)

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[victorjulien]

Merged in #6139, thanks!