Implement integration testing with GitHub actions

[arnaudlh]

As described in: https://github.com/aztfmod/landingzones/blob/master/documentation/test/unit_test.md https://medium.com/@nicolas.yuen/cloud-adoption-framework-unit-and-integration-testing-with-terraform-9594630c123b

And following this example: https://github.com/aztfmod/terraform-azurerm-caf-resource-group

[LaurentLesle]

I propose to implement the following integration tests.

For launchpad_opensource_light

Setup

deploy launchpad opensource_light

Scenarios

Test permutations in sandpit workspace

• rover /tf/caf/launchpads/launchpad_opensource_light apply -var location=westeurope
• rover /tf/caf/launchpads/launchpad_opensource_light apply -var location=westeurope -var convention=cafclassic
• rover /tf/caf/launchpads/launchpad_opensource_light apply -var location=westeurope -var convention=cafclassic =var use_prefrix=false