ampctl trace improvements

[leoyvens]

A few improvements from testing ampctl trace:

1. Add some instrumentation for the footer cache
2. Filter spans on the client to avoid receiving pre-truncated responses

Also fix some AI nonsense:
4. Move all logic into ampctl crate instead of having a separate trace-report crate
5. Stop printing the whole span tree to stdout

[Theodus]

LGTM