Feature: Use git submodule to reference iotedge-lorawan-starterkit for bicep templates

[hocinehacherouf]

Is your feature request related to a problem? Please describe.
To test/dev bicep templates, we have to download the code source of iotedge-lorawan-starterkit to the folder templates/azure

Describe the solution you'd like
We can improve this use case by using git submodules.

Under path templates/azure, add a git submoldule targeting iotedge-lorawan-starterkit:

cd templates/azure

git submodule add https://github.com/Azure/iotedge-lorawan-starterkit.git

Update also the ci job validate_arm_templates:

Replace

IoT-Hub-Portal/.github/workflows/arm-ttk.yml

Lines 42 to 55 in 0bd2bb4

	- uses: actions/[email protected]
	- name: Checkout Azure/arm-ttk
	uses: actions/[email protected]
	with:
	repository: Azure/arm-ttk
	path: arm-ttk
	- name: Checkout Azure/iotedge-lorawan-starterkit
	uses: actions/[email protected]
	with:
	repository: Azure/iotedge-lorawan-starterkit
	ref: dev
	path: templates/iotedge-lorawan-starterkit

By

- uses: actions/checkout@v2
  with:
    submodules: recursive