message: refactor: update tscplugin api to match google3
  PR Close
diff: @@ -51,9 +51,7 @@ interface TscPlugin {
  getNextProgram(): ts.Program;
  - prepareEmit(): {
  - transformers: ts.CustomTransformers,
  - };
  + createTransformers(): ts.CustomTransformers;
  }
  /**
  @@ -106,5 +104,5 @@ export class NgTscPlugin implements TscPlugin {
  getNextProgram(): ts.Program { return this.compiler.getNextProgram(); }
  - prepareEmit(): {transformers: ts.CustomTransformers;} { return this.compiler.prepareEmit(); }
  + createTransformers(): ts.CustomTransformers { return this.compiler.prepareEmit().transformers; }
  }
  