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/+workloads-overview/overview-workload-status.tsx

@@ -8,7 +8,7 @@ import { observer } from "mobx-react";
 import { PieChart } from "../chart";
 import { cssVar } from "../../utils";
 import { ChartData, ChartDataSets } from "chart.js";
-import { themeStore } from "../../theme.store";
+import { ThemeStore } from "../../theme.store";
 
 interface SimpleChartDataSets extends ChartDataSets {
   backgroundColor?: string[];
@@ -41,7 +41,7 @@ export class OverviewWorkloadStatus extends React.Component<Props> {
       labels: [] as string[],
       datasets: [{
         data: [1],
-        backgroundColor: [themeStore.activeTheme.colors.pieChartDefaultColor],
+        backgroundColor: [ThemeStore.getInstance().activeTheme.colors.pieChartDefaultColor],
         label: "Empty"
       }]
     };