Fix autoprovisioning with spot nodes

[avrittrohwer]

Fixes / Features

• Fixes workload rendering when using spot, without this change xpk workload create errors like:

  [XPK] Waiting for `Creating Workload`, for 0 seconds
  error: error parsing /tmp/tmp242uhnfs: error converting YAML to JSON: yaml: line 33: could not find expected ':'
  [XPK] Task: `Creating Workload` terminated with code `1`
  

• Adds required pod tolerations when using node auto-provisioning with spot nodes. Without the tolerations cluster autoscaler will not create new spot node pools.

Testing / Documentation

• [ y ] Tests pass
• [ y, not needed ] Appropriate changes to documentation are included in the PR

Node auto-provisioning with spot

1. Created a xpk cluster with --spot and autoprovisioning flags.
2. Created a workload with a different topology than the cluster default.
3. Observed a nodepool being created with the new workload topology using spot TPU nodes.

Node auto-provisioning without spot

1. Created a xpk cluster with --spot and autoprovisioning flags.
2. Created a workload with a different topology than the cluster default and --on-demand flag.
3. Validated generated YAML does not specify spot node-selector and tolerations
4. Observed a nodepool being created with the new workload topology using on-demand TPU nodes.

Not auto-provisioning with spot

1. Created a xpk cluster with --spot flag.
2. Validated nodepool was created with spot nodes
3. Created a workload and validated it ran.

[avrittrohwer]

zone: 'us-central2'>] finished with error: Try a different location, or try again later: Google Compute Engine does not have enough resources available to fulfill request: us-central2-b