[Feature Request] BREAKING change: Add options to split validation and publication resources

## Description

Add options to have validation and testing separate from the subscription where modules are published.
Assuming that in a ALZ landing zone a sandbox might be required for validation and testing, while published modules/template specs need to go to a separate "Automation" subscription.

If this exists, we need to add guidance for how to set up using a dual subscription setup.

We probably need to consider changing the prefix of the `ARM_*` variables to split the two environments:

- GH: Create separate prefixes for validation and publication:
- `VALIDATION_`
- `PUBLISHING_`
- ADO: Add something like this for `serviceConnections`:
- `serviceConnectionValidation = 'your-servicecon-name'`
- `serviceConnectionPublish = $(serviceConnectionValidation)`