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-pie-charts.tsx

@@ -9,7 +9,7 @@ import { nodesStore } from "../+nodes/nodes.store";
 import { ChartData, PieChart } from "../chart";
 import { ClusterNoMetrics } from "./cluster-no-metrics";
 import { bytesToUnits } from "../../utils";
-import { themeStore } from "../../theme.store";
+import { ThemeStore } from "../../theme.store";
 import { getMetricLastPoints } from "../../api/endpoints/metrics.api";
 
 export const ClusterPieCharts = observer(() => {
@@ -29,7 +29,7 @@ export const ClusterPieCharts = observer(() => {
     const { podUsage, podCapacity } = data;
     const cpuLimitsOverload = cpuLimits > cpuCapacity;
     const memoryLimitsOverload = memoryLimits > memoryCapacity;
-    const defaultColor = themeStore.activeTheme.colors.pieChartDefaultColor;
+    const defaultColor = ThemeStore.getInstance().activeTheme.colors.pieChartDefaultColor;
 
     if (!memoryCapacity || !cpuCapacity || !podCapacity) return null;
     const cpuData: ChartData = {