Improve sampler

[estringana]

Description

There have been error when more than one request was running on parallel due to the sampler not managing it properly. This PR refactor the sampler to stop these errors.

APPSEC-53993

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 77.96%. Comparing base (3053d70) to head (3a9942b).
Report is 2 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2761      +/-   ##
============================================
- Coverage     79.52%   77.96%   -1.57%     
  Complexity     2216     2216              
============================================
  Files           201      227      +26     
  Lines         22619    26644    +4025     
  Branches          0      989     +989     
============================================
+ Hits          17987    20772    +2785     
- Misses         4632     5346     +714     
- Partials          0      526     +526     

Flag	Coverage Δ
appsec-extension	69.19% <ø> (?)
tracer-extension	78.81% <ø> (ø)
tracer-php	80.55% <ø> (ø)

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see 26 files with indirect coverage changes

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