Resolve stalled retrieval requests from network indexers

[jacobheun]

Summary

Update Boost to handle LegsVoucher graphsync requests via the new, unpaid graphsync retrieval pathway rather than falling back to the legacy code path, so that indexers are able to more reliability ingest advertisements and avoid performance impacts on Boost.

Background

In Boost 1.7.0 we released sector monitoring checks for index integrity. This unfortunately had a bug that could accidentally mark a sector as removed. The fix for this was released in Boost 1.7.1.

The side effect for this was that it resulted in the need for indexers to re-ingest advertisement chains for users going from 1.7.0 to 1.7.1 or later. This increase in retrievals from indexers led to an increase in stalled retrieval. While we significantly improved performance in unpaid graphsync retrievals in Boost 1.6.1, the indexer currently uses a LegsVoucher that causes retrieval for indexers to fallback to the legacy retrievals paths - which can result in issues like #1125 and its linked related issues.

The stalled retrievals here, also prevent the indexers from fully ingesting the records, causing end user retrieval discovery to be unreliable as a consequence. Stabilizing these retrievals should improve both end to end retrievability, and reduce performance impacts from stalled retrievals in Boost.