Remove ExtenedMap, ToggleSet, and observable versions (#3310)

- Switch to helper functions instead. They don't impact the prototype
  tree and it means that we don't need to introduce versions that are
  both observable and "normal"

- Tidy <ItemListLayout> and hiddenTableColumns to not need
  pre-initialization

Signed-off-by: Sebastian Malton <sebastian@malton.name>

src/migrations/helpers.ts

@@ -5,7 +5,7 @@
 
 import type Conf from "conf";
 import type { Migrations } from "conf/dist/source/types";
-import { ExtendedMap, iter } from "../common/utils";
+import { getOrInsert, iter } from "../common/utils";
 import { isTestEnv } from "../common/vars";
 
 export function migrationLog(...args: any[]) {
@@ -20,10 +20,10 @@ export interface MigrationDeclaration {
 }
 
 export function joinMigrations(...declarations: MigrationDeclaration[]): Migrations<any> {
-  const migrations = new ExtendedMap<string, ((store: Conf<any>) => void)[]>();
+  const migrations = new Map<string, ((store: Conf<any>) => void)[]>();
 
   for (const decl of declarations) {
-    migrations.getOrInsert(decl.version, () => []).push(decl.run);
+    getOrInsert(migrations, decl.version, []).push(decl.run);
   }
 
   return Object.fromEntries(