Alter query API code to use string for ProjectID instead of int64
We store ProjectID as a string in our trace/log/metrics ClickHouse tables so no changes needed there. Our application code just needs to use strings too, so we can pass in a string ProjectID instead of something that must parse into an int64. This allows us to hash in the instanceID from a self-managed instance to ensure ProjectIDs are unique across all GitLab instances.
Edited by Mat Appelman