Plugin Extensions: Custom limits for extensions-per-plugin (#69430)

* feat(plugins): remove global limit on extensions per placement

* feat: add a way to limit extension per plugin at the getter

* test(plugins): fix failing getPluginExtensions test

* refactor(panelmenu): put back limit of 2 extensions per plugin

* tests: add a test for checking all extensions are returned by default

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Co-authored-by: Jack Westbrook <jack.westbrook@gmail.com>

packages/grafana-runtime/src/services/pluginExtensions/getPluginExtensions.ts

@@ -5,9 +5,11 @@ import { isPluginExtensionComponent, isPluginExtensionLink } from './utils';
 export type GetPluginExtensions<T = PluginExtension> = ({
   extensionPointId,
   context,
+  limitPerPlugin,
 }: {
   extensionPointId: string;
   context?: object | Record<string | symbol, unknown>;
+  limitPerPlugin?: number;
 }) => {
   extensions: T[];
 };