Support ApmTracingMulticonfig in dynamic config

[bwoebi]

RFC: https://docs.google.com/document/d/1J4azr17gJQipGhyWIWuBArkhe1UfStKx7XZRmjqjhqQ/edit?tab=t.b22x9owvguir#heading=h.4ri1ilwwn02m

[datadog-official]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 60.65% (-0.04%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 11fbbd3 | Docs | Datadog PR Page | Was this helpful? React with 👍/👎 or give us feedback!}

[pr-commenter]

Benchmarks [ tracer ]

Benchmark execution time: 2026-04-09 12:42:54

Comparing candidate commit 11fbbd3 in PR branch bob/multi_conf with baseline commit 14dabf8 in branch master.

Found 2 performance improvements and 1 performance regressions! Performance is the same for 191 metrics, 0 unstable metrics.

scenario:EmptyFileBench/benchEmptyFileBaseline-opcache

• 🟥 execution_time [+67.938µs; +367.922µs] or [+2.069%; +11.202%]

scenario:MessagePackSerializationBench/benchMessagePackSerialization

• 🟩 execution_time [-5.807µs; -3.853µs] or [-5.359%; -3.555%]

scenario:MessagePackSerializationBench/benchMessagePackSerialization-opcache

• 🟩 execution_time [-5.541µs; -3.099µs] or [-5.138%; -2.873%]