feat: add standard vnet config file for buildingblock definition

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[JohannesRudolph]

@ishabakeh a few things don't add up here

• why is this called standard-vnet when it is not deploying any vnet?
• there are some issues with the tf code, ie. I it's not clear why I would want to either adopt existing spn/storage account with submodules (e.g. import blocks are an alternative)
• we need to provide clear guidance on the purpose of this module

[ishabakeh]

• The module is the configuration for the standard-vnet BB that we already have
• We are still looking for the best place for this config modules, but in the meantime we wanted to try its functionality with "collie kit import" but the Storage creation module will be moved from here and be another standalone module itself. I'm Thinking that we have separate Storage module for creation of backend module for all building blocks, and for Service principals, it make sense that engineers be able to either try the one they already have from bootstrap (for dev or test purposes) or create a new one right away with minimum effort
• the purpose is to generate backend config and provider credentials and later other pre-requisites for deploying a buildingblock
• Guidance will be also changed and completed