[perf] cap span descendants query, possibly lazy load

[mikeldking]

Some traces can get extremely deep - we need to put a limit on this and consider lazy loading this

[mikeldking]

It looks like the entire span decendents is loaded in a data loader in one go. We need to figure out how the data loader only returns the IDs and to load the content second:

phoenix/src/phoenix/server/api/types/Span.py

Line 198 in 21ca64b

@strawberry.field(

[mikeldking]

Since it's not a connection, we actually don't have a way to cap it right now