[Feature Request]: Validate YAML transforms with a schema

### What would you like to happen?

Currently we have a schema for validating a full pipeline; it would be useful to use this same schema (or the transform subset thereof) to validate YamlTransforms that are used as part of a larger transform.

We could also consider adding transform-specific validation for SchemaTransform-vended providers (e.g. auto-generated based on their config properties).

### Issue Priority

Priority: 3 (nice-to-have improvement)

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