firebase init remoteconfig will always overwrite existing template files

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Found through code analysis. It looks like we overwrite an existing template file regardless of user choice.

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Verified:

$ echo '{"key": "value"}' > remoteconfig.template.json
$ firebase init remoteconfig

     ######## #### ########  ######## ########     ###     ######  ########
     ##        ##  ##     ## ##       ##     ##  ##   ##  ##       ##
     ######    ##  ########  ######   ########  #########  ######  ######
     ##        ##  ##    ##  ##       ##     ## ##     ##       ## ##
     ##       #### ##     ## ######## ########  ##     ##  ######  ########

You're about to initialize a Firebase project in this directory:

  /Users/inlined/git/junkdrawer

Before we get started, keep in mind:

  * You are initializing in an existing Firebase project directory


=== Project Setup

First, let's associate this project directory with a Firebase project.
You can create multiple project aliases by running firebase use --add,
but for now we'll just set up a default project.

i  .firebaserc already has a default project, using inlined-junkdrawer.

=== Remoteconfig Setup
? What file should be used for your Remote Config template? remoteconfig.template.json
? File remoteconfig.template.json already exists. Do you want to overwrite the existing Remote Config template? No

i  Writing configuration info to firebase.json...
i  Writing project information to .firebaserc...

✔  Firebase initialization complete!
$ cat remoteconfig.template.json
$ # nothing printed

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Second error: the default is an empty file, which fails deployment.