Feat: combine service across httproutes expressions

[randmonkey]

What this PR does / why we need it:

Which issue this PR fixes:

Special notes for your reviewer:

PR Readiness Checklist:

Complete these before marking the PR as ready to review:

• the CHANGELOG.md release notes have been updated to reflect any significant (and particularly user-facing) changes introduced by this PR

[codecov]

Codecov Report

Attention: Patch coverage is 81.21547% with 102 lines in your changes missing coverage. Please review.

Project coverage is 58.9%. Comparing base (f187f31) to head (97d56a1).
Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
...al/dataplane/translator/subtranslator/httproute.go	80.4%	72 Missing and 16 partials ⚠️
...l/dataplane/translator/subtranslator/backendref.go	84.6%	9 Missing and 3 partials ⚠️
...ternal/dataplane/translator/translate_httproute.go	87.5%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##            main   #6734      +/-   ##
========================================
- Coverage   77.8%   58.9%   -19.0%     
========================================
  Files        204     205       +1     
  Lines      23870   24183     +313     
========================================
- Hits       18590   14245    -4345     
- Misses      4337    9285    +4948     
+ Partials     943     653     -290     

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[randmonkey]

Superseded by #6766