[Backport 2.x] Added Score Normalization and Combination feature, manual backport

[martin-gaievski]

Description

Backport base PRs related to Hybrid Search feature. One is base big PR, last two are small and only related to feature flag name. Commits history is preserved from main branch

Main PR with porting from feature branch:
61e6e98 from #241

Fix feature flag apporach:
5819df6 from #246

2a9f70a from #247

what is not included:

PR with fixes after testing: #259, it will be done in separate PR.

[codecov]

Codecov Report

Merging #263 (19a321c) into 2.x (5228fc7) will decrease coverage by 3.27%.
Report is 6 commits behind head on 2.x.
The diff coverage is 84.11%.

@@             Coverage Diff              @@
##                2.x     #263      +/-   ##
============================================
- Coverage     89.55%   86.29%   -3.27%     
- Complexity      103      340     +237     
============================================
  Files             7       29      +22     
  Lines           316      992     +676     
  Branches         52      153     +101     
============================================
+ Hits            283      856     +573     
- Misses           16       70      +54     
- Partials         17       66      +49     

Files Changed	Coverage Δ
...earch/neuralsearch/ml/MLCommonsClientAccessor.java	92.00% <ø> (ø)
...nsearch/neuralsearch/query/NeuralQueryBuilder.java	89.01% <ø> (+1.09%)	⬆️
...nsearch/neuralsearch/query/HybridQueryBuilder.java	72.64% <72.64%> (ø)
...lsearch/search/query/HybridQueryPhaseSearcher.java	73.58% <73.58%> (ø)
...ensearch/neuralsearch/query/HybridQueryWeight.java	76.00% <76.00%> (ø)
...euralsearch/search/HybridTopScoreDocCollector.java	79.62% <79.62%> (ø)
...earch/processor/normalization/ScoreNormalizer.java	80.00% <80.00%> (ø)
...ensearch/neuralsearch/query/HybridQueryScorer.java	81.25% <81.25%> (ø)
...r/normalization/L2ScoreNormalizationTechnique.java	83.33% <83.33%> (ø)
...neuralsearch/processor/NormalizationProcessor.java	83.87% <83.87%> (ø)
... and 16 more