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>

integration/__tests__/app.tests.ts

@@ -60,8 +60,8 @@ describe("Lens integration tests", () => {
       it("ensures helm repos", async () => {
         const repos = await listHelmRepositories();
 
-        if (!repos[0]) {
-          fail("Lens failed to add Bitnami repository");
+        if (repos.length === 0) {
+          fail("Lens failed to add any repositories");
         }
 
         await app.client.click("[data-testid=kube-tab]");