Refactor to enforce strictNullChecks

This commit applies `strictNullChecks` to the entire codebase to improve
maintainability and type safety. Key changes include:

- Remove some explicit null-checks where unnecessary.
- Add necessary null-checks.
- Refactor static factory functions for a more functional approach.
- Improve some test names and contexts for better debugging.
- Add unit tests for any additional logic introduced.
- Refactor `createPositionFromRegexFullMatch` to its own function as the
  logic is reused.
- Prefer `find` prefix on functions that may return `undefined` and
  `get` prefix for those that always return a value.

tests/e2e/revert-toggle.cy.ts

@@ -1,3 +1,5 @@
+import { expectExists } from '@tests/shared/Assertions/ExpectExists';
+
 describe('revert toggle', () => {
   context('toggle switch', () => {
     beforeEach(() => {
@@ -30,20 +32,24 @@ describe('revert toggle', () => {
           const font = getFont($label[0]);
           const expectedMinimumTextWidth = getTextWidth(text, font);
           const containerWidth = $label.parent().width();
+          expectExists(containerWidth);
           expect(expectedMinimumTextWidth).to.be.lessThan(containerWidth);
         });
     });
   });
 });
 
-function getFont(element) {
+function getFont(element: Element): string {
   const computedStyle = window.getComputedStyle(element);
   return `${computedStyle.fontWeight} ${computedStyle.fontSize} ${computedStyle.fontFamily}`;
 }
 
-function getTextWidth(text, font) {
+function getTextWidth(text: string, font: string): number {
   const canvas = document.createElement('canvas');
   const ctx = canvas.getContext('2d');
+  if (!ctx) {
+    throw new Error('Unable to get 2D context from canvas element');
+  }
   ctx.font = font;
   const measuredWidth = ctx.measureText(text).width;
   return measuredWidth;