CI: Document the 'all-in-one' layout + small refactoring (#10725)

* Rename aio to all-in-one and document it

ADTM.
Acronyms don't tell much.

* Refactor vm_count in tests provisioning

tests/files/packet_amazon-linux-2-all-in-one.yml

@@ -1,4 +1,4 @@
 ---
 # Instance settings
 cloud_image: amazon-linux-2
-mode: aio
+mode: all-in-one

tests/files/packet_ubuntu20-all-in-one-docker.yml

@@ -1,7 +1,7 @@
 ---
 # Instance settings
 cloud_image: ubuntu-2004
-mode: aio
+mode: all-in-one
 
 # Kubespray settings
 auto_renew_certificates: true

tests/files/packet_ubuntu20-calico-aio-ansible-2_11.yml

@@ -1 +0,0 @@
-packet_ubuntu20-calico-aio.yml

tests/files/packet_ubuntu20-calico-all-in-one-ansible-2_11.yml

@@ -0,0 +1 @@
+packet_ubuntu20-calico-all-in-one.yml

tests/files/packet_ubuntu20-calico-all-in-one-hardening.yml

@@ -1,7 +1,7 @@
 ---
 # Instance settings
 cloud_image: ubuntu-2004
-mode: aio
+mode: all-in-one
 
 # Kubespray settings
 auto_renew_certificates: true

tests/files/packet_ubuntu20-calico-all-in-one.yml

@@ -1,7 +1,7 @@
 ---
 # Instance settings
 cloud_image: ubuntu-2004
-mode: aio
+mode: all-in-one
 
 # Kubespray settings
 auto_renew_certificates: true

tests/files/packet_ubuntu22-all-in-one-docker.yml

@@ -1,7 +1,7 @@
 ---
 # Instance settings
 cloud_image: ubuntu-2204
-mode: aio
+mode: all-in-one
 vm_memory: 1600Mi
 
 # Kubespray settings

tests/files/packet_ubuntu22-calico-all-in-one.yml

@@ -1,7 +1,7 @@
 ---
 # Instance settings
 cloud_image: ubuntu-2204
-mode: aio
+mode: all-in-one
 vm_memory: 1600Mi
 
 # Kubespray settings