add strategy mitogen_linear when installed mitogen (#5985)

* add strategy mitogen_linear when installed mitogen

* add small docs

Rename playbook file

The raw action executes as a regular Mitogen connection, which requires Python on the target, so add strategy: linear to bootstrap-os role playbook.

* add mitogen to  CI test
fix typo

* enable mitogen test on deploy-part1 tests
change version from master to release
download tar.gz archive

* run all CI tests with mitogen

* disable mitogen with upgrade CI tests

* enable mitogen on CI tests via env vars

* disable mitogen on CI test by default, enable on some different OS

* disable mitogen CI test on centos8
(get error  /usr/bin/python: No such file or directory)

upgrade-cluster.yml

@@ -23,6 +23,7 @@
     - { role: bastion-ssh-config, tags: ["localhost", "bastion"] }
 
 - hosts: k8s-cluster:etcd:calico-rr
+  strategy: linear
   any_errors_fatal: "{{ any_errors_fatal | default(true) }}"
   gather_facts: false
   vars: