feat(compiler-cli): make enableIvy ngtsc/true equivalent (#28616)

Currently setting `enableIvy` to true runs a hybrid mode of `ngc` and `ngtsc`. This is counterintuitive given the name of the flag itself.

This PR makes the `true` value equivalent to the previous `ngtsc`, and `ngtsc` becomes an alias for `true`. Effectively this removes the hybrid mode as well since there's no other way to enable it.

PR Close #28616

packages/compiler-cli/src/perform_compile.ts

@@ -120,6 +120,10 @@ export function calcProjectFileAndBasePath(project: string):
 
 export function createNgCompilerOptions(
     basePath: string, config: any, tsOptions: ts.CompilerOptions): api.CompilerOptions {
+  // enableIvy `ngtsc` is an alias for `true`.
+  if (config.angularCompilerOptions && config.angularCompilerOptions.enableIvy === 'ngtsc') {
+    config.angularCompilerOptions.enableIvy = true;
+  }
   return {...tsOptions, ...config.angularCompilerOptions, genDir: basePath, basePath};
 }