Remove the Redis databroker backend. According to
https://www.pomerium.com/docs/internals/data-storage#redis it has been
discouraged since Pomerium v0.18.
Update the config options validation to return an error if "redis" is
set as the databroker storage backend type.
* wip
* wip
* handle wildcards in override name
* remove wait for ready, add comment about sync, force initial sync complete in test
* address comments
* refactor backend, implement encrypted store
* refactor in-memory store
* wip
* wip
* wip
* add syncer test
* fix redis expiry
* fix linting issues
* fix test by skipping non-config records
* fix backoff import
* fix init issues
* fix query
* wait for initial sync before starting directory sync
* add type to SyncLatest
* add more log messages, fix deadlock in in-memory store, always return server version from SyncLatest
* update sync types and tests
* add redis tests
* skip macos in github actions
* add comments to proto
* split getBackend into separate methods
* handle errors in initVersion
* return different error for not found vs other errors in get
* use exponential backoff for redis transaction retry
* rename raw to result
* use context instead of close channel
* store type urls as constants in databroker
* use timestampb instead of ptypes
* fix group merging not waiting
* change locked names
* update GetAll to return latest record version
* add method to grpcutil to get the type url for a protobuf type
