fix(@schematics/angular): use service decorator in ng generate

Updates the `service` schematic in `ng generate` to use the `@Service` decorator instead of `@Injectable`.

Author: crisbeto

packages/schematics/angular/service/files/__name@dasherize__.__type@dasherize__.ts.template

@@ -1,8 +1,6 @@
-import { Injectable } from '@angular/core';
+import { Service } from '@angular/core';
 
-@Injectable({
-  providedIn: 'root',
-})
+@Service()
 export class <%= classifiedName %> {
 
 }

packages/schematics/angular/service/index_spec.ts

@@ -36,6 +36,7 @@ describe('Service Schematic', () => {
     skipPackageJson: false,
   };
   let appTree: UnitTestTree;
+
   beforeEach(async () => {
     appTree = await schematicRunner.runSchematic('workspace', workspaceOptions);
     appTree = await schematicRunner.runSchematic('application', appOptions, appTree);
@@ -50,12 +51,13 @@ describe('Service Schematic', () => {
     expect(files).toContain('/projects/bar/src/app/foo/foo.ts');
   });
 
-  it('service should be tree-shakeable', async () => {
+  it('should use @Service decorator', async () => {
     const options = { ...defaultOptions };
 
     const tree = await schematicRunner.runSchematic('service', options, appTree);
     const content = tree.readContent('/projects/bar/src/app/foo/foo.ts');
-    expect(content).toMatch(/providedIn: 'root',/);
+    expect(content).toMatch(/@Service\(\)/);
+    expect(content).toMatch(/import \{ Service \} from '@angular\/core'/);
   });
 
   it('should respect the skipTests flag', async () => {

packages/schematics/angular/service/schema.json

@@ -1,48 +1,48 @@
 {
   "$schema": "http://json-schema.org/draft-07/schema",
-  "$id": "SchematicsAngularService",
-  "title": "Angular Service Options Schema",
+  "$id": "SchematicsAngularInjectable",
+  "title": "Angular Injectable Options Schema",
   "type": "object",
   "additionalProperties": false,
-  "description": "Creates a new service in your project. Services are used to encapsulate reusable logic, such as data access, API calls, or utility functions. This schematic simplifies the process of generating a new service with the necessary files and boilerplate code.",
+  "description": "Creates a new injectable in your project. Injectables are used to encapsulate reusable logic, such as data access, API calls, or utility functions. This schematic simplifies the process of generating a new injectable with the necessary files and boilerplate code.",
   "properties": {
     "name": {
       "type": "string",
-      "description": "The name for the new service. This will be used to create the service's class and spec files (e.g., `my-service.service.ts` and `my-service.service.spec.ts`).",
+      "description": "The name for the new injectable. This will be used to create the injectable class and spec files (e.g., `my-inj.service.ts` and `my-inj.service.spec.ts`).",
       "$default": {
         "$source": "argv",
         "index": 0
       },
-      "x-prompt": "What name would you like to use for the service?"
+      "x-prompt": "What name would you like to use for the injectable?"
     },
     "path": {
       "type": "string",
       "$default": {
         "$source": "workingDirectory"
       },
-      "description": "The path where the service files should be created, relative to the workspace root. If not provided, the service will be created in the project's `src/app` directory.",
+      "description": "The path where the injectable files should be created, relative to the workspace root. If not provided, the injectable will be created in the project's `src/app` directory.",
       "visible": false
     },
     "project": {
       "type": "string",
-      "description": "The name of the project where the service should be added. If not specified, the CLI will determine the project from the current directory.",
+      "description": "The name of the project where the injectable should be added. If not specified, the CLI will determine the project from the current directory.",
       "$default": {
         "$source": "projectName"
       }
     },
     "flat": {
       "type": "boolean",
       "default": true,
-      "description": "Creates files at the top level of the project or the given path. If set to false, a new folder with the service's name will be created to contain the files."
+      "description": "Creates files at the top level of the project or the given path. If set to false, a new folder with the injectable's name will be created to contain the files."
     },
     "skipTests": {
       "type": "boolean",
-      "description": "Skip the generation of a unit test file `spec.ts` for the service.",
+      "description": "Skip the generation of a unit test file `spec.ts` for the injectable.",
       "default": false
     },
     "type": {
       "type": "string",
-      "description": "Append a custom type to the service's filename. For example, if you set the type to `service`, the file will be named `my-service.service.ts`."
+      "description": "Append a custom type to the injectable's filename. For example, if you set the type to `service`, the file will be named `my-inj.service.ts`."
     },
     "addTypeToClassName": {
       "type": "boolean",