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/integration/infrastructure/RuntimeSanity/Validators/ValidatorTestRunner.ts

@@ -4,9 +4,6 @@ import { ISanityValidator } from '@/infrastructure/RuntimeSanity/Common/ISanityV
 export function itNoErrorsOnCurrentEnvironment(
   factory: () => ISanityValidator,
 ) {
-  if (!factory) {
-    throw new Error('missing factory');
-  }
   it('it does report errors on current environment', () => {
     // arrange
     const validator = factory();