message: refactor(ivy): allow `ImportManager` to have configurable prefix
  The ngcc compiler will want to specify its own prefix when rendering
  definitions.
  PR Close
diff: @@ -52,11 +52,11 @@ export class ImportManager {
  private moduleToIndex = new Map<string, string>();
  private nextIndex = 0;
  - constructor(private isCore: boolean) {}
  + constructor(private isCore: boolean, private prefix = 'i') {}
  generateNamedImport(moduleName: string, symbol: string): string {
  if (!this.moduleToIndex.has(moduleName)) {
  - this.moduleToIndex.set(moduleName, `i${this.nextIndex++}`);
  + this.moduleToIndex.set(moduleName, `${this.prefix}${this.nextIndex++}`);
  }
  if (this.isCore && moduleName === '@angular/core' && !CORE_SUPPORTED_SYMBOLS.has(symbol)) {
  throw new Error(`Importing unexpected symbol ${symbol} while compiling core`);
  