chore(tests): migrate to isolated and simplify TestUDPIngressEssentials

[programmer04]

What this PR does / why we need it:

Tests for UDP in KIC are historically overall complex, they use CoreDNS for verification. This reworks TestUDPIngressEssentials to use an isolated tests framework and makes it much simpler. Instead of CoreDNS it uses kong/go-echo:0.3.0.

Which issue this PR fixes:

Done during work on #5715.
There is also an initiative to get rid of CoreDNS in tests entirely.

Special notes for your reviewer:

What it tests is quite similar to #5724 (previously with Core DNS also such similarity existed) for now I haven't decided to merge them into one test, but I think it's something to consider

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.3%. Comparing base (02dca39) to head (385911c).
Report is 2 commits behind head on main.

❗ Current head 385911c differs from pull request most recent head e4e896b. Consider uploading reports for the commit e4e896b to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #5743     +/-   ##
=======================================
+ Coverage   71.7%   73.3%   +1.5%     
=======================================
  Files        175     175             
  Lines      18141   18141             
=======================================
+ Hits       13023   13306    +283     
+ Misses      4174    3858    -316     
- Partials     944     977     +33     

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