Performance/Webpack: Introduces more aggressive code-splitting and other perf improvements (#18544)

* Performance/Webpack: Introduces more aggressive code-splitting and other perf improvements
- Introduces dynamic imports for built-in plugins
- Uses dynamic imports for various packages (rst2html, brace)
- Introduces route-based dynamic imports
- Splits angular and moment into separate bundles

public/app/features/datasources/NewDataSourcePage.tsx

@@ -131,6 +131,7 @@ class NewDataSourcePage extends PureComponent<Props> {
             className="btn btn-inverse"
             href="https://grafana.com/plugins?type=datasource&utm_source=new-data-source"
             target="_blank"
+            rel="noopener"
           >
             Find more data source plugins on grafana.com
           </a>
@@ -198,6 +199,7 @@ const DataSourceTypeCard: FC<DataSourceTypeCardProps> = props => {
             className="btn btn-inverse"
             href={`${learnMoreLink}?utm_source=grafana_add_ds`}
             target="_blank"
+            rel="noopener"
             onClick={onLearnMoreClick}
           >
             Learn more <i className="fa fa-external-link add-datasource-item-actions__btn-icon" />