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/cluster-issues.tsx

@@ -11,7 +11,7 @@ import { eventStore } from "../+events/event.store";
 import { autobind, cssNames, prevDefault } from "../../utils";
 import { ItemObject } from "../../item.store";
 import { Spinner } from "../spinner";
-import { themeStore } from "../../theme.store";
+import { ThemeStore } from "../../theme.store";
 import { lookupApiLink } from "../../api/kube-api";
 import { kubeSelectedUrlParam, showDetails } from "../kube-object";
 
@@ -145,7 +145,7 @@ export class ClusterIssues extends React.Component<Props> {
           sortByDefault={{ sortBy: sortBy.object, orderBy: "asc" }}
           sortSyncWithUrl={false}
           getTableRow={this.getTableRow}
-          className={cssNames("box grow", themeStore.activeTheme.type)}
+          className={cssNames("box grow", ThemeStore.getInstance().activeTheme.type)}
         >
           <TableHead nowrap>
             <TableCell className="message">Message</TableCell>