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.

src/application/Parser/NodeValidation/NodeValidator.ts

@@ -32,7 +32,7 @@ export class NodeValidator {
     return this;
   }
 
-  public throw(errorMessage: string) {
+  public throw(errorMessage: string): never {
     throw new NodeDataError(errorMessage, this.context);
   }
 }