Auth is not a function when using compatibility in production build

### Version info

**Angular:** 13.3.0

**Firebase:** ^9.8.1

**AngularFire:** 7.3.0

**Other (e.g. Ionic/Cordova, Node, browser, operating system):**

### How to reproduce these conditions

**Steps to set up and reproduce**

When a production build is served, we have an error with Firebase app.auth() is not found. This does not happen with a development build.

We are using the compatibility version of Angular Fire.

### Debug output

** Errors in the JavaScript console **

> main.ts:16 TypeError: Bt.auth is not a function
> at angular-fire-compat-auth.js:59:51
> at rr.invoke (zone.js:409:30)
> at rr.run (zone.js:169:47)
> at value (core.mjs:25486:28)
> at angular-fire-compat-auth.js:59:23
> at tn (angular-fire-compat.js:147:29)
> at we (angular-fire-compat-auth.js:58:116)
> at new Ue (angular-fire-compat-firestore.js:513:13)
> at Object.$e.ɵfac [as factory] (angular-fire-compat-firestore.js:584:1)
> at value (core.mjs:11477:35)

### Expected behavior

Build runs on both development and production

### Actual behavior

Build runs only in development

issue に記載されている production build を、main.ts:16 と angular-fire-compat-auth.js:59 での失敗から開始して再現します。development bundle と production bundle を比較し、compatibility auth API が存在しない理由を特定します。production build と development の両方で認証が正常に初期化されれば完了です。

索引モデルが issue の本文から書いたものです。