Update rules to correctly resolve to default values

What does this MR do and why?

Implements runtime evaluation for dynamic input rules. Rules are validated at parse time (!209948 (merged)) but weren't being evaluated when pipelines are created - this MR adds that evaluation.

When a user writes:

cloud_provider: { default: 'aws' }
instance_type:
  rules:
    - if: '$[[ inputs.cloud_provider ]] == "aws"'
      default: 't3.micro'

instance_type will resolves to t3.micro based on cloud_provider: 'aws'

References

#568903

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