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

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 61.92%. Comparing base (3076898) to head (bb55152). :warning: Report is 73 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3281      +/-   ##
==========================================
- Coverage   61.93%   61.92%   -0.02%     
==========================================
  Files         140      140              
  Lines       12356    12356              
  Branches     1616     1616              
==========================================
- Hits         7653     7651       -2     
- Misses       3992     3995       +3     
+ Partials      711      710       -1     

see 1 file with indirect coverage changes

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[pr-commenter[bot]]

Benchmarks [ tracer ]

Benchmark execution time: 2025-07-24 19:08:08

Comparing candidate commit bb55152a2538bbe5859cac9f344e0c6af2cefff4 in PR branch ben.db/APMAPI-1266-knuth-sampling with baseline commit 3076898282b38d87007e47bd5a27a143e0e760b1 in branch master.

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

scenario:PHPRedisBench/benchRedisOverhead

• 🟥 execution_time [+32.963µs; +60.172µs] or [+2.120%; +3.869%]