[BUG FIX] [ANDROID] Add check google-services plugin does not exist

[lucaboy]

No description provided.

[billmote]

When would this apply? The included marketingcloudsdk.gradle adds the dependency for you and then the plugin is applied.

[lucaboy]

If there is another library that add the same plugin before your gradle plugin is applied, you'll get the following error: "Cannot add extension with name 'googleServices', as there is an extension already registered with that name" and the build will fail.

[jefflnorton]

This may be useful if this plugin is added to an Ionic Capacitor project. In this case the Capacitor project will apply the plugin in the app module.

[cabelotaina]

In cordova-android 9 I made:

<preference name="GradlePluginGoogleServicesEnabled" value="false" />

[dtarnawsky]

Any update on whether this PR can be included in a release?