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/unit/presentation/bootstrapping/Modules/RuntimeSanityValidator.spec.ts

@@ -10,7 +10,7 @@ describe('RuntimeSanityValidator', () => {
       validateEnvironmentVariables: true,
       validateWindowVariables: true,
     };
-    let actualOptions: ISanityCheckOptions;
+    let actualOptions: ISanityCheckOptions | undefined;
     const validatorMock = (options) => {
       actualOptions = options;
     };