Continue searching backend even if a trace is found in the ingesters

[joe-elliott]

Is your feature request related to a problem? Please describe.
As part of our plans to support "exhaustive search" for traces let's search the backend even if the ingesters return a result. This is related to #161.

Describe the solution you'd like
Continue searching the backend even if the ingesters succeed and combine the results.

Additional context
@annanay25 we need to consider this as we move forward with the query frontend. I'm thinking we will add a number of parameters to the GET /api/traces/xxxxxx endpoint that the query frontend can use for sharding like:

GET /api/traces/xxx?startblock=xxx&endblock=xxx&ingesters=false

By default the /api/traces/xxx endpoint should just search everything.

[annanay25]

I'm thinking we will add a number of parameters to the GET /api/traces/xxxxxx endpoint that the query frontend can use for sharding

Precisely what I was thinking as well. I'll have something more concrete to share soon.

[joe-elliott]

Fixed in #489