search-blitz: add queries for megarepo on k8s.sgdev.org

Created by: ggilmore

This PR adds queries that target the github.com/sgtest/megarepo forks on k8s.sgdev.org:

• https://k8s.sgdev.org/megarepo-normal-indexing (using the normal indexing strategy)
• https://k8s.sgdev.org/megarepo-incremental-indexing-fork (using the experimental delta indexing strategy).

This allows us to collect metrics that allow us to compare search times that use two use two different indexing strategies.

Test plan

search-blitz has its own unit tests