aws: master: change instances types from xen to nitro (KVM)

This updates the AWS instances types from xen to the more up to date nitro (KVM) platform. In addition to being more up to date and better performance, it resolves a current issue where xen instance type VMs do not come up after zypper update. https://bugzilla.suse.com/show_bug.cgi?id=1196403

All instance types are chosen from the officially certified ones on https://aws.amazon.com/sap/instance-types/. https://github.com/SUSE/ha-sap-terraform-deployments/pull/822/commits/fa42aa776cc81f0cd9eac2a53b81254449ad5aaa
Disk naming conventions need to be adapted as xen uses a different naming scheme than nitro (KVM). https://github.com/SUSE/ha-sap-terraform-deployments/pull/822/commits/6afd9ac9f5593f79a80f255a250e797b8451912e
Forward port common_variables['drbd'] from develop to fix non-existing sbd_storage_type in case of iscsi+drdb deployment. fa42aa7

SUSE / ha-sap-terraform-deployments

aws: master: change instances types from xen to nitro (KVM) #822