Change dataLayer Variable Name

### Expected Behaviour

I may want to change the name of the dataLayer variable. For example, if an implementor already has Google Tag Manager implemented, and they are looking to implement an Adobe Client Data Layer, they will have to deal with a naming conflict between the Adobe Client Data Layer and GTM's built-in DataLayer. We have a few choices to fix this:

1. Rip & remove all GTM code
2. Rename GTM's DataLayer, then rewrite the server-side GTM push code and implement the Adobe Client Data Layer
3. Rename the Adobe Client Data Layer and initially keep the GTM code in place before sunsetting once the new tracking is fully implemented

To support option # 3, there would need to be some way to pass a new dataLayer name to the Adobe Client Data Layer.

### Actual Behaviour

There appears to be no way to chage dataLayer variable name

### Reproduce Scenario (including but not limited to)

N/A

#### Steps to Reproduce

N/A

#### Platform and Version

1.0.0.beta2

#### Sample Code that illustrates the problem

N/A

#### Logs taken while reproducing problem

N/A

The issue names no files, tests, or entry points; begin by locating the existing dataLayer implementation and its public configuration or initialization path. Define the supported naming behavior and verify that an Adobe Client Data Layer can use a custom variable name without conflicting with Google Tag Manager.

Written by the indexing model from the issue text.