Allow more than one instance of this extension on a single VM

I know that the [documentation](https://docs.microsoft.com/en-us/azure/virtual-machines/extensions/custom-script-linux) states...

> You can have only one version of an extension applied to the VM. To run a second custom script, you can update the existing extension with a new configuration. Alternatively, you can remove the custom script extension and reapply it with the updated script.

... but i found this behaviour to be extremely inconvenient.

When you work on VMs as a Team, one team member might introduce a custom-script extension doing task A, while another creates one to do task B. They can all life in peace, until they want to deploy them on the same VM.

Un-Installing the first one is not a suitable solution since:

- it make's it harder to debug, since there is no trace of the extension being installed
- Languages like Terraform do not natively support deleting ressources after first provisioning, creating a need for hacky workarounds

Merging to extensions into a single one is painfull as well, if you've been using the "script" parameter in both extensions, which only supports a single script.

I would greatly appreciate it, if this behaviour could be changed! 💛