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/presentation/components/Scripts/View/Tree/TreeView/Bindings/TreeInputFilterEvent.ts

@@ -1,9 +1,15 @@
 import type { ReadOnlyTreeNode } from '../Node/TreeNode';
 
-export interface TreeViewFilterEvent {
-  readonly action: TreeViewFilterAction;
-  readonly predicate?: TreeViewFilterPredicate;
-}
+type TreeViewFilterTriggeredEvent = {
+  readonly action: TreeViewFilterAction.Triggered;
+  readonly predicate: TreeViewFilterPredicate;
+};
+
+type TreeViewFilterRemovedEvent = {
+  readonly action: TreeViewFilterAction.Removed;
+};
+
+export type TreeViewFilterEvent = TreeViewFilterTriggeredEvent | TreeViewFilterRemovedEvent;
 
 export enum TreeViewFilterAction {
   Triggered,
@@ -14,14 +20,14 @@ export type TreeViewFilterPredicate = (node: ReadOnlyTreeNode) => boolean;
 
 export function createFilterTriggeredEvent(
   predicate: TreeViewFilterPredicate,
-): TreeViewFilterEvent {
+): TreeViewFilterTriggeredEvent {
   return {
     action: TreeViewFilterAction.Triggered,
     predicate,
   };
 }
 
-export function createFilterRemovedEvent(): TreeViewFilterEvent {
+export function createFilterRemovedEvent(): TreeViewFilterRemovedEvent {
   return {
     action: TreeViewFilterAction.Removed,
   };