ref(autofix): migrate to EAP and continuous profiling (#97430)

- Migrates Autofix's trace context from the Transactions dataset to
Spans since the former will be deprecated soon
- Refactors Explorer's profile-fetching utils so Autofix can re-use them
for continuous profiles

Sorry for the large diff, but most of it is moving stuff between files
and re-doing tests.

Author: roaga