[BUG] Test Connection is not working for multi data source

[bandinib-amzn]

Describe the bug

After introducing the change in PR #5895, Test connection is no longer working.

To Reproduce
Steps to reproduce the behavior:

1. Go to Create data source
2. Enter title, endpoint, credentials.
3. Click on 'Test connection'
4. See error

Expected behavior
Test connection should be successful for correct credentials and endpoint.

OpenSearch Version
N/A

Dashboards Version
N/A

Plugins

N/A

Screenshots

[bandinib-amzn]

This is due to missing customApiSchemaRegistryPromise while calling dataSourceServiceSetup.getDataSourceClient in https://github.com/opensearch-project/OpenSearch-Dashboards/blob/main/src/plugins/data_source/server/routes/test_connection.ts#L62-L72

Argument of type '{ savedObjects: SavedObjectsClientContract; cryptography: CryptographyServiceSetup; dataSourceId: string | undefined; testClientDataSourceAttr: DataSourceAttributes; request: OpenSearchDashboardsRequest<...>; authRegistry: IAuthenticationMethodRegistery; }' is not assignable to parameter of type 'DataSourceClientParams'.
  Property 'customApiSchemaRegistryPromise' is missing in type '{ savedObjects: SavedObjectsClientContract; cryptography: CryptographyServiceSetup; dataSourceId: string | undefined; testClientDataSourceAttr: DataSourceAttributes; request: OpenSearchDashboardsRequest<...>; authRegistry: IAuthenticationMethodRegistery; }' but required in type 'DataSourceClientParams'.

cc: @BionIT

[BionIT]

This is due to missing customApiSchemaRegistryPromise while calling dataSourceServiceSetup.getDataSourceClient in https://github.com/opensearch-project/OpenSearch-Dashboards/blob/main/src/plugins/data_source/server/routes/test_connection.ts#L62-L72

Argument of type '{ savedObjects: SavedObjectsClientContract; cryptography: CryptographyServiceSetup; dataSourceId: string | undefined; testClientDataSourceAttr: DataSourceAttributes; request: OpenSearchDashboardsRequest<...>; authRegistry: IAuthenticationMethodRegistery; }' is not assignable to parameter of type 'DataSourceClientParams'.
  Property 'customApiSchemaRegistryPromise' is missing in type '{ savedObjects: SavedObjectsClientContract; cryptography: CryptographyServiceSetup; dataSourceId: string | undefined; testClientDataSourceAttr: DataSourceAttributes; request: OpenSearchDashboardsRequest<...>; authRegistry: IAuthenticationMethodRegistery; }' but required in type 'DataSourceClientParams'.

cc: @BionIT

@bandinib-amzn yeah, I had a PR to fix it - no one reviewed yet https://github.com/opensearch-project/OpenSearch-Dashboards/pull/5944/files