drag n drop bounding characters (pgsql fix) (#14376)

* specifies object handling for all current providers

* implements the same for column dragndrop

* adjusted test

* adds pgsql provider name constant

src/sql/platform/connection/common/constants.ts

@@ -11,6 +11,7 @@ export const outputChannelName = 'MSSQL';
 export const capabilitiesOptions = 'OPTIONS_METADATA';
 
 export const mssqlProviderName = 'MSSQL';
+export const pgsqlProviderName = 'PGSQL';
 export const anyProviderName = '*';
 export const connectionProviderContextKey = 'connectionProvider';