Remove AgentTracer.noopScope() sentinel

[mcculls]

Motivation

This helps with switching between the two context manager approaches, since the checks now don't assume a particular implementation.

Additional Notes

To be merged in once #12008 is merged

Contributor Checklist

• Format the title according to the contribution guidelines
• Assign the type: and (comp: or inst:) labels in addition to any other useful labels
• Avoid using close, fix, or any linking keywords when referencing an issue
  Use solves instead, and assign the PR milestone to the issue
• Update the CODEOWNERS file on source file addition, migration, or deletion
• Update public documentation with any new configuration flags or behaviors
• Once approved, use merge queue to merge the PR

Jira ticket: [PROJ-IDENT]

[datadog-official]

Removing the exported AgentTracer.noopScope() method is source- and binary-incompatible for custom instrumentations compiled against the current bootstrap API: an upgraded agent can throw NoSuchMethodError when that instrumentation loads or calls the method. The replacement public NoopScope singleton requires downstream recompilation and does not preserve existing callers.

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[mhlidd]

LGTM

[datadog-official]

🎯 Code Coverage (details)
• Patch Coverage: 33.33%
• Overall Coverage: 57.11% (-12.62%)

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[dd-octo-sts]

🟢 Java Benchmark SLOs — All performance SLOs passed

Suite	Status
Startup	🟢 pass

SLO thresholds are defined here based on automatically generated metrics. A warning is raised when results are within 5% of the threshold.

PR vs. master results

Scenario	Candidate	master	Δ (95% CI of mean)
startup:insecure-bank:iast:Agent	13.92 s	13.87 s	[-0.4%; +1.1%] (no difference)
startup:insecure-bank:tracing:Agent	12.89 s	12.97 s	[-1.5%; +0.3%] (no difference)
startup:petclinic:appsec:Agent	16.78 s	16.65 s	[+0.0%; +1.5%] (maybe worse)
startup:petclinic:iast:Agent	16.81 s	16.84 s	[-1.3%; +0.9%] (no difference)
startup:petclinic:profiling:Agent	15.93 s	16.40 s	[-8.8%; +3.1%] (unstable)
startup:petclinic:sca:Agent	16.32 s	16.75 s	[-6.9%; +1.8%] (no difference)
startup:petclinic:tracing:Agent	16.05 s	16.05 s	[-1.1%; +1.0%] (no difference)

Commit: 5ba19eaa · CI Pipeline · Benchmarking Platform UI

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