feat(ivy): do not emit empty providers/imports for defineInjector (#29598)

The defineInjector function specifies its providers and imports array to
be optional, so if no providers/imports are present these keys may be
omitted. This commit updates the compiler to only generate the keys when
necessary.

PR Close #29598

packages/compiler-cli/src/ngtsc/annotations/src/ng_module.ts

@@ -158,10 +158,8 @@ export class NgModuleDecoratorHandler implements DecoratorHandler<NgModuleAnalys
       schemas: [],
     };
 
-    const providers: Expression = ngModule.has('providers') ?
-        new WrappedNodeExpr(ngModule.get('providers') !) :
-        new LiteralArrayExpr([]);
     const rawProviders = ngModule.has('providers') ? ngModule.get('providers') ! : null;
+    const providers = rawProviders !== null ? new WrappedNodeExpr(rawProviders) : null;
 
     // At this point, only add the module's imports as the injectors' imports. Any exported modules
     // are added during `resolve`, as we need scope information to be able to filter out directives