Add 'validate' parameter to use during releases

**Is your feature request related to a problem? Please describe.**
Add a new parameter to be used during deployments and releases which can be used to set parameters or transform text within the helper during a release, e.g. changing `az deployment group create` to `az deployment group create` during the **TestWebApp / Validation** workflow.

**Describe the solution you'd like**
Add a parameter that can be passed into the workflow to toggle behaviour for deployment testing. See https://github.com/Azure/AKS-Construction/pull/642/files for how to pass the parameter into PlayWright.

**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features you've considered.

**Additional context**
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