Template structure updates

[simarbir]

Description of changes: Updated the template structure, with the following changes:

• The existing-vpc-entrypoint template is now re-named to be called workload stack and is called from the main new-vpc-entrypoint template.
• The new-vpc-entrypoint template no longer directly calls the instance and TGW templates, instead just the VPC and the workload templates are called.
• The template structure/hierarchy now looks like below: -> quickstart-cisco-meraki-sdwan-vmx-entrypoint-new-vpc.template.yaml --> VPC stack --> quickstart-cisco-meraki-sdwan-vmx-workload.template.yaml (also used for existing vpc deployments) ---> quickstart-cisco-meraki-sdwan-vmx-instance.yaml ---> quickstart-cisco-meraki-sdwan-vmx-tgw.yaml

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[simarbir]

@sshvans - updated the template structure based on the feedback, please let me know if this looks okay to you, thanks.

[mufaddalq]

@sshvans - updated the template structure based on the feedback, please let me know if this looks okay to you, thanks.

@sshvans : Reminder to review and merge. Thanks