Drop CentOS 8 Stream nodesets and sanity checks

CentOS 8 Stream has been EOLd and our mirror automatically replicated
the empty package repo state set by upstream. The end result is that no
jobs that rely on this platform are able to run successfully any longer.
In preparation for removing these images entirely from zuul+nodepool we
remove the nodesets. We also remove some sanity checks in base jobs that
were geared towards moving people from CentOS 8 to CentOS 8 Stream. At
this point that is all moot and we shouldn't need it any longer.

Note I didn't split the base job change into a test change and a
production update change because all we're doing is removing some tasks.
This seems safe as these tasks shouldn't side effect in functional jobs.

Change-Id: I36baa3079e818b6504afcc6fe3743d3ec7de99eb

playbooks/base-test/pre.yaml

@@ -5,30 +5,6 @@
       zuul_log_path_shard_build: true
     - log-inventory
 
-# NOTE(ianw) 2022-02-09 : centos8 had a hard shutdown at upstream EOL
-# that some were not prepared for.  We can't remove the node-type
-# because that gives a Zuul error, preventing projects merging changes
-# to update their node types (see
-# 2c05c44c32db895d2a793265fb86b6bf662c32d0).  We've removed all the
-# CentOS 8 builds in nodepool and the centos-8 node label is pointing
-# at centos-8-stream.  But to get people moving off this, we fail jobs
-# explicitly using the default nodeset with a name of "centos-8" that
-# points to a image of type "centos-8-stream".
-#
-# This way people can set their jobs non-voting as they merge changes
-# to explicitly move away from centos-8 node type.  We obviously hope
-# to remove this hack ASAP.
-- hosts: all
-  name: Hard fail CentOS 8 nodes
-  tasks:
-    - name: Fail CentOS 8 nodes
-      fail:
-        msg: "The centos-8 node type is no longer supported.  You need to switch this job to use a centos-8-stream node type."
-      when:
-        - item == 'centos-8'
-        - hostvars[item]['nodepool']['label'] == 'centos-8-stream'
-      loop: "{{ query('inventory_hostnames', 'all,!localhost') }}"
-
 - hosts: all
   name: Setup Zuul environment
   pre_tasks:

playbooks/base/pre.yaml

@@ -5,30 +5,6 @@
       zuul_log_path_shard_build: true
     - log-inventory
 
-# NOTE(ianw) 2022-02-09 : centos8 had a hard shutdown at upstream EOL
-# that some were not prepared for.  We can't remove the node-type
-# because that gives a Zuul error, preventing projects merging changes
-# to update their node types (see
-# 2c05c44c32db895d2a793265fb86b6bf662c32d0).  We've removed all the
-# CentOS 8 builds in nodepool and the centos-8 node label is pointing
-# at centos-8-stream.  But to get people moving off this, we fail jobs
-# explicitly using the default nodeset with a name of "centos-8" that
-# points to a image of type "centos-8-stream".
-#
-# This way people can set their jobs non-voting as they merge changes
-# to explicitly move away from centos-8 node type.  We obviously hope
-# to remove this hack ASAP.
-- hosts: all
-  name: Hard fail CentOS 8 nodes
-  tasks:
-    - name: Fail CentOS 8 nodes
-      fail:
-        msg: "The centos-8 node type is no longer supported.  You need to switch this job to use a centos-8-stream node type."
-      when:
-        - item == 'centos-8'
-        - hostvars[item]['nodepool']['label'] == 'centos-8-stream'
-      loop: "{{ query('inventory_hostnames', 'all,!localhost') }}"
-
 - hosts: all
   name: Setup Zuul environment
   pre_tasks:

zuul.d/nodesets.yaml

@@ -1,22 +1,4 @@
 # Shared nodesets for all tenants
-- nodeset:
-    name: centos-8
-    nodes:
-      - name: centos-8
-        label: centos-8-stream
-
-- nodeset:
-    name: centos-8-stream
-    nodes:
-      - name: centos-8-stream
-        label: centos-8-stream
-
-- nodeset:
-    name: centos-8-stream-arm64
-    nodes:
-      - name: centos-8-stream-arm64
-        label: centos-8-stream-arm64
-
 - nodeset:
     name: centos-9-stream
     nodes: