Fetch trace entries asynchronously

This change is a preparation for the intergaration with
perfetto's trace processor (TP), because trace entries coming
from perfetto are going to be fetched through asynchronous
calls to the TP WebWorker (WASM).

Test: npm run test:all
Bug: b/284424874
Change-Id: Ife5d47b07902b31992d4f81f15580d44016df37f
69 files changed