Fixing Singleton typing to correctly return child class (#1914)

- Add distinction between `getInstance` and `getInstanceOrCreate` since
  it is not always possible to create an instance (since you might not
  know the correct arguments)

- Remove all the `export const *Store = *Store.getInstance<*Store>();`
  calls as it defeats the purpose of `Singleton`. Plus with the typing
  changes the appropriate `*Store.getInstance()` is "short enough".

- Special case the two extension export facades to not need to use
  `getInstanceOrCreate`. Plus since they are just facades it is always
  possible to create them.

- Move some other types to be also `Singleton`'s: ExtensionLoader,
  ExtensionDiscovery, ThemeStore, LocalizationStore, ...

- Fixed dev-run always using the same port with electron inspect

- Update Store documentation with new recommendations about creating
  instances of singletons

- Fix all unit tests to create their dependent singletons

Signed-off-by: Sebastian Malton <sebastian@malton.name>

src/renderer/components/cluster-settings/cluster-settings.tsx

@@ -1,5 +1,5 @@
 import React from "react";
-import { clusterStore } from "../../../common/cluster-store";
+import { ClusterStore } from "../../../common/cluster-store";
 import { ClusterProxySetting } from "./components/cluster-proxy-setting";
 import { ClusterNameSetting } from "./components/cluster-name-setting";
 import { ClusterHomeDirSetting } from "./components/cluster-home-dir-setting";
@@ -13,7 +13,7 @@ import { CatalogEntity } from "../../api/catalog-entity";
 
 
 function getClusterForEntity(entity: CatalogEntity) {
-  const cluster = clusterStore.getById(entity.metadata.uid);
+  const cluster = ClusterStore.getInstance().getById(entity.metadata.uid);
 
   if (!cluster?.enabled) {
     return null;