platforms, tmt: Rename and restructure cloud variants

We now have more than one cloud system that is essentially a KVM
environment that uses cloud-init to boot, so now we declare that
"generic" and have the OpenStack and Oracle images reuse those
definitions.

Also, in preparation for layered cloud image variants, rename
them from "Cloud-" to "Cloud-Base-". Vagrant variants are
similarly prefixed to make it clear who provides them.

Finally, restructure the layout of the tmt plans to match the
description structure.

tmt/plans/build-vagrant-libvirt.fmf

@@ -1,8 +0,0 @@
-summary: Build Vagrant image for libvirt
-discover:
-    how: fmf
-environment:
-    image_type: oem
-    image_profile: Vagrant-libvirt
-execute:
-    how: tmt

tmt/plans/cloud/base/build-aws.fmf

@@ -1,8 +1,8 @@
-summary: Build OpenStack image
+summary: Build AWS EC2 base image
 discover:
     how: fmf
 environment:
     image_type: oem
-    image_profile: Cloud-OpenStack
+    image_profile: Cloud-Base-AmazonEC2
 execute:
     how: tmt

tmt/plans/cloud/base/build-azure.fmf

@@ -1,8 +1,8 @@
-summary: Build Azure image
+summary: Build Azure base image
 discover:
     how: fmf
 environment:
     image_type: oem
-    image_profile: Cloud-Azure
+    image_profile: Cloud-Base-Azure
 execute:
     how: tmt

tmt/plans/cloud/base/build-gcp.fmf

@@ -1,8 +1,8 @@
-summary: Build GCP image
+summary: Build GCP base image
 discover:
     how: fmf
 environment:
     image_type: oem
-    image_profile: Cloud-GCE
+    image_profile: Cloud-Base-GCE
 execute:
     how: tmt

tmt/plans/cloud/base/build-generic.fmf

@@ -1,8 +1,8 @@
-summary: Build AWS EC2 image
+summary: Build Generic base image
 discover:
     how: fmf
 environment:
     image_type: oem
-    image_profile: Cloud-AmazonEC2
+    image_profile: Cloud-Base-Generic
 execute:
     how: tmt

tmt/plans/vagrant/base/build-libvirt.fmf

@@ -0,0 +1,8 @@
+summary: Build base Vagrant image for libvirt
+discover:
+    how: fmf
+environment:
+    image_type: oem
+    image_profile: Cloud-Base-Vagrant-libvirt
+execute:
+    how: tmt

tmt/plans/vagrant/base/build-virtualbox.fmf

@@ -1,4 +1,4 @@
-summary: Build Vagrant image for VirtualBox
+summary: Build base Vagrant image for VirtualBox
 discover:
     how: fmf
 adjust:
@@ -6,6 +6,6 @@ adjust:
     when: arch != x86_64
 environment:
     image_type: oem
-    image_profile: Vagrant-VirtualBox
+    image_profile: Cloud-Base-Vagrant-VirtualBox
 execute:
     how: tmt