Fix drop chunks for chunk with multiple top level

[VianneyRuhlmann]

What does this PR do?

Fix a bug in drop chunks for chunks with several top-level spans which is causing chunks to be kept when they could be dropped. Agent logic is here

Motivation

What inspired you to submit this pull request?

Additional Notes

Anything else we should know when reviewing?

How to test the change?

Describe here in detail how the change can be validated.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.93%. Comparing base (c365938) to head (7ce4ba8).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1288      +/-   ##
==========================================
+ Coverage   71.91%   71.93%   +0.02%     
==========================================
  Files         368      368              
  Lines       58146    58175      +29     
==========================================
+ Hits        41814    41849      +35     
+ Misses      16332    16326       -6     

Components	Coverage Δ
datadog-crashtracker	50.65% <ø> (-0.03%)	⬇️
datadog-crashtracker-ffi	5.86% <ø> (ø)
datadog-alloc	98.73% <ø> (ø)
data-pipeline	87.86% <ø> (ø)
data-pipeline-ffi	88.19% <ø> (ø)
ddcommon	84.31% <ø> (ø)
ddcommon-ffi	73.84% <ø> (ø)
ddtelemetry	59.98% <ø> (ø)
ddtelemetry-ffi	21.24% <ø> (ø)
dogstatsd-client	83.26% <ø> (ø)
datadog-ipc	82.39% <ø> (ø)
datadog-profiling	76.90% <ø> (ø)
datadog-profiling-ffi	62.12% <ø> (ø)
datadog-sidecar	37.24% <ø> (ø)
datdog-sidecar-ffi	13.71% <ø> (ø)
spawn-worker	55.18% <ø> (ø)
tinybytes	92.44% <ø> (ø)
datadog-trace-normalization	98.24% <ø> (ø)
datadog-trace-obfuscation	94.17% <ø> (ø)
datadog-trace-protobuf	59.65% <ø> (ø)
datadog-trace-utils	90.04% <100.00%> (+0.04%)	⬆️
datadog-tracer-flare	61.03% <ø> (ø)
datadog-log	75.57% <ø> (ø)

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