fix(compiler): recover from structural errors in watch mode (#19953)

This also changes the compiler so that we throw less often
on structural changes and produce a meaningful state
in the `ng.Program` in case of errors.

Related to #19951

PR Close #19953

packages/compiler-cli/test/ngc_spec.ts

@@ -1464,7 +1464,7 @@ describe('ngc transformer command-line', () => {
       const messages: string[] = [];
       const exitCode =
           main(['-p', path.join(basePath, 'src/tsconfig.json')], message => messages.push(message));
-      expect(exitCode).toBe(2, 'Compile was expected to fail');
+      expect(exitCode).toBe(1, 'Compile was expected to fail');
       expect(messages[0]).toContain(['Tagged template expressions are not supported in metadata']);
     });