Refactor schematic-auth into schematic-setup

[anngvu]

Currently, this Action furnishes a config.yml and Google auth token and has both as required inputs (via workflow secrets). The rationale for having this be an independent action was that some workflows that use schematic may or may not need these additional files (e.g. schema convert does not need these files). However, configuring these files should probably be part in the new setup-schematic Action via optional inputs.