CI jobs for [AETHER-778], [AETHER-779] and [AETHER-782]

- Leverages the name-extension to create new jobs
- Introduces a new pipeline job for tost builds
- Same job is used for post-merge and nightly builds
- Passes the DOCKER_TAG as env variable
- Disables versioning jobs for TOST

The new jobs are currently disabled to avoid any service
disruption during the transition. Will follow another patch
that will disable the old jobs and enable the new ones.

Change-Id: I82e023609693b37d310f735f818c3659c84ccf79
diff --git a/jjb/defaults.yaml b/jjb/defaults.yaml
index b867c9b..fa39327 100644
--- a/jjb/defaults.yaml
+++ b/jjb/defaults.yaml
@@ -57,6 +57,9 @@
     # used to rename jobs if required
     name-extension: ''
 
+    # used to disable a job
+    disable-job: false
+
     # regexes for branch matching
     all-branches-regexp: '.*'
     supported-branches-regexp: '.*'