[Profiler] Little improvement

[gleocadie]

Summary of changes

Use only one container in Sample class to store labels.

Reason for change

There is 2 types of labels: numeric and string. The type is related to the type of the value.
Before that we had 2 containers (one per type of label).

Implementation details

• Use std::variant to store NumericLabel and StringLabel labels in the same container.
• Use std::visit to have a processing per label type.
• Rename Label into StringLabel
• Remove SpanLabel and use NumericLabel instead (since it's a Numeric label)

Test coverage

Current test should be suffice

Other details

[datadog-datadog-prod-us1]

Datadog Report

All test runs 274a1e0 🔗

✅ 2 Total Test Services: 0 Failed, 2 Passed

Test Services

Service Name	Failed	Known Flaky	New Flaky	Passed	Skipped	Total Time	Test Service View
dd-trace-dotnet	0	0	0	247940	2932	23h 1m 17.72s	Link
exploration_tests	0	0	0	22085	3	2m 14.08s	Link

[andrewlock]

Execution-Time Benchmarks Report ⏱️

Execution-time results for samples comparing the following branches/commits:

• This PR (6830)
• master

Execution-time benchmarks measure the whole time it takes to execute a program. And are intended to measure the one-off costs. Cases where the execution time results for the PR are worse than latest master results are shown in red. The following thresholds were used for comparing the execution times:

• Welch test with statistical test for significance of 5%
• Only results indicating a difference greater than 5% and 5 ms are considered.

Note that these results are based on a single point-in-time result for each branch. For full results, see the dashboard.

Graphs show the p99 interval based on the mean and StdDev of the test run, as well as the mean value of the run (shown as a diamond below the graph).

gantt
    title Execution time (ms) FakeDbCommand (.NET Framework 4.6.2) 
    dateFormat  X
    axisFormat %s
    todayMarker off
    section Baseline
    This PR (6830) - mean (71ms)  : 66, 75
     .   : milestone, 71,
    master - mean (69ms)  : 67, 72
     .   : milestone, 69,

    section CallTarget+Inlining+NGEN
    This PR (6830) - mean (1,001ms)  : 975, 1028
     .   : milestone, 1001,
    master - mean (999ms)  : 978, 1020
     .   : milestone, 999,

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gantt
    title Execution time (ms) FakeDbCommand (.NET Core 3.1) 
    dateFormat  X
    axisFormat %s
    todayMarker off
    section Baseline
    This PR (6830) - mean (103ms)  : 101, 106
     .   : milestone, 103,
    master - mean (103ms)  : 100, 106
     .   : milestone, 103,

    section CallTarget+Inlining+NGEN
    This PR (6830) - mean (692ms)  : 671, 713
     .   : milestone, 692,
    master - mean (691ms)  : 672, 711
     .   : milestone, 691,

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gantt
    title Execution time (ms) FakeDbCommand (.NET 6) 
    dateFormat  X
    axisFormat %s
    todayMarker off
    section Baseline
    This PR (6830) - mean (90ms)  : 88, 93
     .   : milestone, 90,
    master - mean (90ms)  : 88, 92
     .   : milestone, 90,

    section CallTarget+Inlining+NGEN
    This PR (6830) - mean (645ms)  : 630, 660
     .   : milestone, 645,
    master - mean (646ms)  : 629, 662
     .   : milestone, 646,

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gantt
    title Execution time (ms) HttpMessageHandler (.NET Framework 4.6.2) 
    dateFormat  X
    axisFormat %s
    todayMarker off
    section Baseline
    This PR (6830) - mean (189ms)  : 185, 192
     .   : milestone, 189,
    master - mean (189ms)  : 184, 195
     .   : milestone, 189,

    section CallTarget+Inlining+NGEN
    This PR (6830) - mean (1,099ms)  : 1075, 1123
     .   : milestone, 1099,
    master - mean (1,099ms)  : 1070, 1128
     .   : milestone, 1099,

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gantt
    title Execution time (ms) HttpMessageHandler (.NET Core 3.1) 
    dateFormat  X
    axisFormat %s
    todayMarker off
    section Baseline
    This PR (6830) - mean (268ms)  : 263, 272
     .   : milestone, 268,
    master - mean (268ms)  : 264, 272
     .   : milestone, 268,

    section CallTarget+Inlining+NGEN
    This PR (6830) - mean (870ms)  : 845, 896
     .   : milestone, 870,
    master - mean (870ms)  : 845, 895
     .   : milestone, 870,

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gantt
    title Execution time (ms) HttpMessageHandler (.NET 6) 
    dateFormat  X
    axisFormat %s
    todayMarker off
    section Baseline
    This PR (6830) - mean (260ms)  : 256, 264
     .   : milestone, 260,
    master - mean (260ms)  : 256, 264
     .   : milestone, 260,

    section CallTarget+Inlining+NGEN
    This PR (6830) - mean (859ms)  : 824, 894
     .   : milestone, 859,
    master - mean (855ms)  : 825, 885
     .   : milestone, 855,

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[datadog-ddstaging]

Datadog Report

Branch report: gleocadie/refactor-labels-in-sample-class
Commit report: 274a1e0
Test service: dd-trace-dotnet

✅ 0 Failed, 12 Passed, 0 Skipped, 0s Total Time

[chrisnas]

LGTM