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>

docs/extensions/guides/main-extension.md

@@ -45,8 +45,6 @@ It accesses some Lens state data, and it periodically logs the name of the clust
 ```typescript
 import { LensMainExtension, Store } from "@k8slens/extensions";
 
-const clusterStore = Store.clusterStore
-
 export default class ActiveClusterExtensionMain extends LensMainExtension {
 
   timer: NodeJS.Timeout
@@ -54,11 +52,11 @@ export default class ActiveClusterExtensionMain extends LensMainExtension {
   onActivate() {
     console.log("Cluster logger activated");
     this.timer = setInterval(() => {
-      if (!clusterStore.active) {
+      if (!Store.ClusterStore.getInstance().active) {
         console.log("No active cluster");
         return;
       }
-      console.log("active cluster is", clusterStore.active.contextName)
+      console.log("active cluster is", Store.ClusterStore.getInstance().active.contextName)
     }, 5000)
   }