Use stricter typings for the NgModule decorator options, not an any array

Which @angular/* package(s) are relevant/releated to the feature request?

core

Description

The NgModule interface is used as options for the @NgModule() decorator and accepts any[] for various properties, it should use stricter typings.

This is the current interface:

export declare interface NgModule {
  /* ... */
  declarations?: Array<Type<any> | any[]>;
  imports?: Array<Type<any> | ModuleWithProviders<{}> | any[]>;
  /* ... */
  exports?: Array<Type<any> | any[]>;
  entryComponents?: Array<Type<any> | any[]>;
  bootstrap?: Array<Type<any> | any[]>;
  schemas?: Array<SchemaMetadata | any[]>;
  /* ... */
}

It would be a breaking change, but it would also help TSC provide better suggestions like this, where I’ve provided a function reference instead of calling the .forRoot() static method of a module:

Error: web/src/app/app.module.ts:15:7 - error TS2322: Type '() => ModuleWithProviders<MyExampleModule>' is not assignable to type 'Type<any> | ModuleWithProviders<{}>'.
  Property 'ngModule' is missing in type '() => ModuleWithProviders<MyExampleModule>' but required in type 'ModuleWithProviders<{}>'.

15       MyExampleModule.forRoot,
         ~~~~~~~~~~~~~~~~~~~~~~~

  node_modules/@angular/core/core.d.ts:4749:5
    4749     ngModule: Type<T>;
             ~~~~~~~~
    'ngModule' is declared here.
  web/src/app/app.module.ts:15:7
    15       MyExampleModule.forRoot,
             ~~~~~~~~~~~~~~~~~~~~~~~
    Did you mean to call this expression?

Proposed solution

Replace any[] with a stricter type, and maybe even use a helper type alias like this one:

export type ListEntryOrList<T> = T | T[];

If the above mentioned type alias would be used, then the inteface would look something like this:

export declare interface NgModule {
  /* ... */
  declarations?: ListEntryOrList<Type<any>>[];
  imports?: ListEntryOrList<Type<any> | ModuleWithProviders<{}>>[];
  /* ... */
  exports?: ListEntryOrList<Type<any>>[];
  entryComponents?: ListEntryOrList<Type<any>>[];
  bootstrap?: ListEntryOrList<Type<any>>[];
  schemas?: ListEntryOrList<SchemaMetadata>[];
  /* ... */
}

This sullution assumes that the any is not really any. If other values are accepted, like factory functions, those could be included in the updated/stricter type definition.

Alternatives considered

You can avoid arrays, but that beats the purpose of having the support for arrays in the first place.

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