Add validation for single node clusters

[shreyas-goenka]

Changes

This PR adds a warning validating that the configuration for a single node cluster is valid for interactive, job, job-task, and pipeline clusters.

Note: We skip the validation if a cluster policy is configured because the policy is likely to configure spark_conf / custom_tags itself.

Note: Terrform originally only had validation for interactive, job, and job-task clusters. This PR adding the validation for pipeline clusters as well is new.

This PR follows the same logic as we used to have in Terraform. The validation was removed from Terraform because we had no way to demote the error to a warning: https://github.com/databricks/terraform-provider-databricks/pull/4222

Background

Single-node clusters require spark_conf and custom_tags to be correctly set in the cluster definition for them to function optimally. The cluster will be created even if incorrectly configured, but its performance will not be great.

For example, if both spark_conf and custom_tags are not set and num_workers is 0, then only the driver process will be launched on the cluster compute instance thus leading to sub-optimal utilization of available compute resources and no parallelization across worker processes when processing a spark query.

Issue

This PR addresses some issues reported in https://github.com/databricks/cli/issues/1546

Tests

Unit tests and manually.

Example output of the warning:

➜  bundle-playground git:(master) ✗ cli bundle validate
Warning: Single node cluster is not correctly configured
  at resources.pipelines.bar.clusters[0]
  in databricks.yml:29:11

num_workers should be 0 only for single-node clusters. To create a
valid single node cluster please ensure that the following properties
are correctly set in the cluster specification:

  spark_conf:
    spark.databricks.cluster.profile: singleNode
    spark.master: local[*]

  custom_tags:
    ResourceClass: SingleNode

Name: foobar
Target: default
Workspace:
  User: shreyas.goenka@databricks.com
  Path: /Workspace/Users/shreyas.goenka@databricks.com/.bundle/foobar/default

Found 1 warning

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Inputs:

• PR number: 1909
• Commit SHA: 382a4efd6efb98adbc7532a3286d81521c899843

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[eng-dev-ecosystem-bot]

Test Details: go/deco-tests/11974490258