Chore: Add initial/experimental xorm spanner driver (#101398)

* make it build and start

* run some migrations

* add build tags, remove log

* remove unused code

* revert go.mod changes

* move initialisation into dialect file

* update workspace

* update workspace once again

* clean up dependencies

* further cleanup

* Address some review feedback.

* Fix go.sum.

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Co-authored-by: Peter Štibraný <pstibrany@gmail.com>

pkg/services/sqlstore/database_config.go

@@ -203,6 +203,8 @@ func (dbCfg *DatabaseConfig) buildConnectionString(cfg *setting.Cfg, features fe
 		}
 
 		cnnstr += buildExtraConnectionString('&', dbCfg.UrlQueryParams)
+	case migrator.Spanner:
+		cnnstr = dbCfg.Name
 	default:
 		return fmt.Errorf("unknown database type: %s", dbCfg.Type)
 	}