Remove v1 pipeline logic from data pipeline

[stephen-soltesz]

Because the data pipeline co-existed with two versions v1 & v2, and now that the v1 data pipeline is decommissioned, we can begin deleting code relevant only to the v1 pipeline. This issue will track that effort.

• [x] Delete Task queues in all projects.
• [x] Remove functions
• [x] Remove obsolete flags
• [x] Remove dependencies on annotation-service repo
• [x] Remove WEB-INF directory
• [x] Remove Legacy/Annotation rows from Pipeline: overview dashboard
• [x] Deploy all changes to production and verify no regressions

[stephen-soltesz]

https://github.com/m-lab/etl/releases/tag/prod-v2.21.0

[stephen-soltesz]

Complete for etl repo.

[stephen-soltesz]

This issue will track remove v1 logic from the gardener component also.

• [x] Add go.mod support to gardener
• [x] Unused flags and environment variable dependencies
• [x] Eliminate (if obsolete) or consolidate datastore saver logic
• [x] Eliminate unused state package (e.g. state.DatastoreSaver appears redundant)
• [x] Eliminate unused cloud/bq/sanity.go logic
• [x] Remove v1 client logic in client package and handler