Remove auto-value-annotation dependency from firebase-common

[samtstern]

[READ] Step 1: Are you in the right place?

Yes.

[REQUIRED] Step 2: Describe your environment

• Android Studio version: any
• Firebase Component: common
• Component version: 18.0.0.

[REQUIRED] Step 3: Describe the problem

Steps to reproduce:

If you look at https://dl.google.com/dl/android/maven2/com/google/firebase/firebase-common/18.0.0/firebase-common-18.0.0.pom

You can see this dependency:

    <dependency>
      <groupId>com.google.auto.value</groupId>
      <artifactId>auto-value-annotations</artifactId>
      <version>1.6.3</version>
      <scope>compile</scope>
      <type>jar</type>
    </dependency>

This adds a new dependency (a 5kB JAR so not a big one) to every app that uses Firebase:
https://mvnrepository.com/artifact/com.google.auto.value/auto-value-annotations/1.6.3'

I believe it also causes issues with apps that are using auto-value at a different version than we are:
google/auto#620

We only use this dependency inside common in one place:
https://github.com/firebase/firebase-android-sdk/blob/master/firebase-common/src/main/java/com/google/firebase/platforminfo/LibraryVersion.java

We would probably be better off just hand-writing the value class and dropping the dep.

Relevant Code:

N/A

[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.

[vkryachko]

Fixed by #1472