rust: remove unused

[catenacyber]

Link to redmine ticket:
None, generic cleaning

Describe changes:

• rust: remove unused dead code

Found with
git grep 'pub ' rust/src/ | cut -d: -f1 | uniq | xargs sed -i -e 's/pub /pub(crate) /' then see rust warnings when compiling

There is nothing more to be done :

• There are parsed fields which get never used. (like rrclass in DNSQueryEntry) : I feel good to keep them
• get_child_value and append_hex are kept for API completeness

Completes #8976

[codecov]

Codecov Report

Merging #9014 (e1b137c) into master (14ecfeb) will decrease coverage by 0.13%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #9014      +/-   ##
==========================================
- Coverage   82.31%   82.18%   -0.13%     
==========================================
  Files         969      969              
  Lines      273559   273573      +14     
==========================================
- Hits       225171   224833     -338     
- Misses      48388    48740     +352     

Flag	Coverage Δ
fuzzcorpus	64.25% <ø> (-0.43%)	⬇️
suricata-verify	60.45% <ø> (-0.03%)	⬇️
unittests	62.93% <ø> (+<0.01%)	⬆️

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

[suricata-qa]

WARNING:

field	baseline	test	%
	SURI_TLPR1_stats_chk
.flow.memuse	519171056	742435272	143.0%

Pipeline 14447

[catenacyber]

Replaced by #9020