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.
