Relax adaptive sampling dependency on sampler tags

[yurishkuro]

Which problem is this PR solving?

• Part of Adaptive sampling does not work with OTEL SDKs #6700

Description of the changes

• Introduce an opt-in option to allow the engine to operate without sampler tags

How was this change tested?

• TBD

[codecov]

Codecov Report

Attention: Patch coverage is 78.57143% with 3 lines in your changes missing coverage. Please review.

Project coverage is 95.96%. Comparing base (24dfa4f) to head (d8b0bcf).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...pling/samplingstrategy/adaptive/post_aggregator.go	66.66%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6692      +/-   ##
==========================================
- Coverage   95.98%   95.96%   -0.02%     
==========================================
  Files         363      363              
  Lines       20608    20606       -2     
==========================================
- Hits        19780    19775       -5     
- Misses        632      634       +2     
- Partials      196      197       +1     

Flag	Coverage Δ
badger_v1	9.82% <ø> (ø)
badger_v2	1.82% <ø> (ø)
cassandra-4.x-v1-manual	14.79% <ø> (ø)
cassandra-4.x-v2-auto	1.81% <ø> (ø)
cassandra-4.x-v2-manual	1.81% <ø> (ø)
cassandra-5.x-v1-manual	14.79% <ø> (ø)
cassandra-5.x-v2-auto	1.81% <ø> (ø)
cassandra-5.x-v2-manual	1.81% <ø> (ø)
elasticsearch-6.x-v1	19.12% <ø> (ø)
elasticsearch-7.x-v1	19.20% <ø> (ø)
elasticsearch-8.x-v1	19.37% <ø> (ø)
elasticsearch-8.x-v2	1.82% <ø> (ø)
grpc_v1	10.80% <ø> (ø)
grpc_v2	7.80% <ø> (ø)
kafka-3.x-v1	10.12% <ø> (ø)
kafka-3.x-v2	1.82% <ø> (ø)
memory_v2	1.82% <ø> (ø)
opensearch-1.x-v1	19.25% <ø> (ø)
opensearch-2.x-v1	19.25% <ø> (ø)
opensearch-2.x-v2	1.82% <ø> (ø)
tailsampling-processor	0.48% <ø> (ø)
unittests	94.85% <78.57%> (-0.02%)	⬇️

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