src: trace_event: secondary storage for metadata

Metadata trace-events should be held in secondary storage so that they can be periodically reemitted. This change establishes the secondary storage and ensures that events are reemitted on each flush.

/cc @nodejs/trace-events

CI:

• https://ci.nodejs.org/job/node-test-pull-request/15041/
• https://ci.nodejs.org/job/node-test-pull-request/15640/
• https://ci.nodejs.org/job/node-test-pull-request/17751/

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines