[BUG] pkg/trace/metrics/timing is leaking a goroutine

[crobert-1]

Agent Environment

N/A

Describe what happened:
While working on open-telemetry/opentelemetry-collector-contrib#30438, goleak detected a leaking goroutine. This is happening due to an indirect dependency on the timing package.

Here's the output of goleak:

 Goroutine 70 in state select, with github.com/DataDog/datadog-agent/pkg/trace/metrics/timing.(*Set).Autoreport.func1 on top of the stack:
github.com/DataDog/datadog-agent/pkg/trace/metrics/timing.(*Set).Autoreport.func1()
        /Users/crobert/go/pkg/mod/github.com/!data!dog/datadog-agent/pkg/trace@v0.50.2/metrics/timing/timing.go:59 +0xed
created by github.com/DataDog/datadog-agent/pkg/trace/metrics/timing.(*Set).Autoreport in goroutine 1
        /Users/crobert/go/pkg/mod/github.com/!data!dog/datadog-agent/pkg/trace@v0.50.2/metrics/timing/timing.go:54 +0x96

Describe what you expected:
No leaking goroutines. The impact here is leaked memory usage upon shutdown. Since this is happens when timing is an indirect dependency there's no access to timing.Stop().

Steps to reproduce the issue:
import "github.com/DataDog/datadog-agent/pkg/trace/agent"

Additional environment details (Operating System, Cloud provider, etc):
Related to #13934
Here's a more in-depth explanation around an identical issue that is in OpenCensus.