Add knuth sampling formula

[genesor]

Description

This PR changes the current sampling formula to the one used in every tracer in order to have consistent sampling.

The tracer now applies sampling decisions for distributed traces missing the sampling decision.

Reviewer checklist

• Test coverage seems ok.
• Appropriate labels assigned.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.28%. Comparing base (86b1fc6) to head (875af45).
Report is 7 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3281      +/-   ##
============================================
- Coverage     75.00%   73.28%   -1.73%     
  Complexity     2969     2969              
============================================
  Files           119      146      +27     
  Lines         11685    16134    +4449     
  Branches          0     1110    +1110     
============================================
+ Hits           8764    11823    +3059     
- Misses         2921     3734     +813     
- Partials          0      577     +577     

Flag	Coverage Δ
appsec-extension	68.71% <ø> (?)
tracer-php	75.01% <ø> (+0.01%)	⬆️

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see 28 files with indirect coverage changes

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[pr-commenter]

Benchmarks [ tracer ]

Benchmark execution time: 2025-06-11 09:40:37

Comparing candidate commit 875af45 in PR branch ben.db/APMAPI-1266-knuth-sampling with baseline commit 86b1fc6 in branch master.

Found 1 performance improvements and 0 performance regressions! Performance is the same for 177 metrics, 0 unstable metrics.

scenario:MessagePackSerializationBench/benchMessagePackSerialization

• 🟩 execution_time [-7.172µs; -6.128µs] or [-3.260%; -2.786%]

[bwoebi]

Looks good :-)