Model changes for k8s

[johnbradley]

High Level Changes

• Renames models and moves data around to better describe jobs that are run on VMs and k8s containers
• Changes to API to provide the k8s specific data for those types of jobs

Model changes

• Renames VMFlavor to JobFlavor and adds memory field to represent cpu/memory for either VM or Container
• Adds cluster_type field to LandoConnection to denote what version of lando(k8s or VM) is servicing that connection
• Renames VMSettings to VMCommand and removes name field.
• Creates K8sStepCommand which contains image name, command, cpu, memory to be used in a k8s step
• Creates K8sCommandSet which contains the set of K8sStepCommand to be used for a job.
• Creates JobSettings model that takes the place of VMSettings. This has a name field, a LandoConnection and either a VMCommand or a K8sCommandSet. This also does validation based on the LandoConnection cluster type(vm/k8s).
• renames VMStrategy to JobStrategy
• renames existing vm_* model fields their new job_* counterparts.

See data/models.py

Remaining "vm" model changes

• JobStrategy still has a volume_mounts field that is not used by k8s jobs. We could move to this to VMCommand.
• CloudSettings is really VM specific. Perhaps we should rename this to VMCloudSettings or OpenStackCloudSettings.
• Job still has some fields that are vm specific: vm_instance_name,vm_volume_name, and vm_volume_mounts. vm_instance_name,vm_volume_name are written to when a job is started and may change if a job is restarted. vm_volume_mounts is just a copy of the values from JobQuestionnaire/JobStrategy.

API Changes

Adds changes to maintain the existing v1 API. This is currently used by lando and bespin-ui. Updates v2 API to have all functionality of v1 API and new field name changes. (Mostly "job" instead of vm"). Lando will start using the v2 api.

Thoughts

I think this PR is way too big. Changing field/model names ripples through the API so the changes are far reaching.

[johnbradley]

Changes based on meeting with @dleehr

• VMCommand renamed to JobRuntimeOpenstack
• K8sCommandSet renamed to JobRuntimeK8s
• K8sStepCommand renamed to JobRuntimeStepK8s
• JobRuntimeStepK8s will use JobFlavor to specify cpu/memory
• CloudSettings renamed to CloudSettingsOpenStack