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/application/Context/State/Code/Event/CodeChangedEvent.spec.ts

@@ -166,6 +166,17 @@ describe('CodeChangedEvent', () => {
     });
   });
   describe('getScriptPositionInCode', () => {
+    it('throws if script is unknown', () => {
+      // arrange
+      const expectedError = 'Unknown script: Position could not be found for the script';
+      const unknownScript = new ScriptStub('1');
+      const sut = new CodeChangedEventBuilder()
+        .build();
+      // act
+      const act = () => sut.getScriptPositionInCode(unknownScript);
+      // assert
+      expect(act).to.throw(expectedError);
+    });
     it('returns expected position for existing script', () => {
       // arrange
       const script = new ScriptStub('1');