dsconfig.json implementation in datasources

[yesoreyeram]

• [do not merge] dsconfig: base grafana-prometheus-datasource#213
• dsconfig: base grafana-loki-datasource#116
• dsconfig: base grafana-tempo-datasource#216
• dsconfig: base github-datasource#771
• dsconfig: base grafana-infinity-datasource#1728
• dsconfig: base google-bigquery-datasource#529
• https://github.com/grafana/mock-datasource/pull/192