Change how subnet is calculated from vnet.
Move all locals about network and IP to a dedicated file.
Improve the terraform code documentation.

t3a.small is not a supported size by sles4sap 15sp5. Change to a size that is
valid for majority of modern sles4sap.

* Manage terraform AWS IP address and ranges

Move all the locals about ip address and ranges to a dedicated file.
Change indentation to split long lines.
Create intermediate new locals to make algorithm hopefully more readable.
Start considering 4 initial IP address that AWS reserve.
Calculate each range and IP dinamically using the previous one as
starting point.

* Improve documentation of AWS network file

* Reduce subnet address range

Use proper default for the iscsi machine type

Add suggestion in CONTRIBUTING about PR preparation

Use full name for lvol abd lvg Ansible tasks
Fix space and indentation
Add missing task names

Fix Ansible lint error and typo