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/shared/Stubs/LocationOpsStub.ts

@@ -24,14 +24,16 @@ export class LocationOpsStub
       methodName: 'combinePaths',
       args: pathSegments,
     });
-    if (this.sequence.length > 0) {
-      return this.sequence.pop();
+    const nextInSequence = this.sequence.pop();
+    if (nextInSequence) {
+      return nextInSequence;
     }
     const key = LocationOpsStub.getScenarioKey(pathSegments);
-    if (!this.scenarios.has(key)) {
-      return pathSegments.join('/PATH-SEGMENT-SEPARATOR/');
+    const foundScenario = this.scenarios.get(key);
+    if (foundScenario) {
+      return foundScenario;
     }
-    return this.scenarios.get(key);
+    return pathSegments.join('/PATH-SEGMENT-SEPARATOR/');
   }
 
   private static getScenarioKey(paths: string[]): string {