ui: Change type of uiTrackIdByTraceTrackId

a `Map` does not preserve type during serialisation+deserialisation

```
const m1 = new Map<number, string>();
const m2 = JSON.parse(JSON.stringify(m1));
console.log(m1);
console.log(m2);
```

Will output:

```
[LOG]: Map (0) {}
[LOG]: {}
```

Bug: 216626668
Change-Id: Ia84e0d47012f9891e56ad86226f37d382b752423
8 files changed
tree: 0e30f532dfc9f48952e73fb164335f3a24ca796f
  1. .github/
  2. bazel/
  3. build_overrides/
  4. buildtools/
  5. debian/
  6. docs/
  7. examples/
  8. gn/
  9. include/
  10. infra/
  11. protos/
  12. python/
  13. src/
  14. test/
  15. tools/
  16. ui/
  17. .clang-format
  18. .clang-tidy
  19. .gitattributes
  20. .gitignore
  21. .gn
  22. .style.yapf
  23. Android.bp
  24. Android.bp.extras
  25. BUILD
  26. BUILD.extras
  27. BUILD.gn
  28. CHANGELOG
  29. codereview.settings
  30. DIR_METADATA
  31. heapprofd.rc
  32. LICENSE
  33. meson.build
  34. METADATA
  35. MODULE_LICENSE_APACHE2
  36. OWNERS
  37. perfetto.rc
  38. PerfettoIntegrationTests.xml
  39. PRESUBMIT.py
  40. README.chromium
  41. README.md
  42. TEST_MAPPING
  43. traced_perf.rc
  44. WORKSPACE
README.md

Perfetto - System profiling, app tracing and trace analysis

Perfetto is a production-grade open-source stack for performance instrumentation and trace analysis. It offers services and libraries and for recording system-level and app-level traces, native + java heap profiling, a library for analyzing traces using SQL and a web-based UI to visualize and explore multi-GB traces.

See https://perfetto.dev/docs or the /docs/ directory for documentation.