Angular 20 update (#2854)

# Pull Request

## 🤨 Rationale

Fixes #2829

## 👩‍💻 Implementation

- Updated Angular dependencies to 20.3.15
- Updated to Angular-20-compatible `eslint-config-angular` version
- Updated forked Angular files in
`packages/angular-workspace/nimble-angular/thirdparty`

## 🧪 Testing

Automated tests pass.

Author: m-akinc

change/@ni-nimble-angular-94411da5-6376-458f-b07b-e3af6e9c35f7.json

@@ -0,0 +1,7 @@
+{
+  "type": "major",
+  "comment": "Angular 20 update",
+  "packageName": "@ni/nimble-angular",
+  "email": "7282195+m-akinc@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}

change/@ni-ok-angular-cb089779-4479-42e3-b63e-a2e68cadd349.json

@@ -0,0 +1,7 @@
+{
+  "type": "major",
+  "comment": "Angular 20 update",
+  "packageName": "@ni/ok-angular",
+  "email": "7282195+m-akinc@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}

change/@ni-spright-angular-c931d952-f56b-45e7-a5fd-dfd7350b26f6.json

@@ -0,0 +1,7 @@
+{
+  "type": "major",
+  "comment": "Angular 20 update",
+  "packageName": "@ni/spright-angular",
+  "email": "7282195+m-akinc@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}