Add run_shell_script and pip_install_requirements utility steps

[bdalpe]

Summary

Adds support for two additional Prefect deployment utility pull steps in Terraform deployment configuration:

• run_shell_script
• pip_install_requirements

This updates deployment pull_steps so these step types can be configured in Terraform and correctly serialized/deserialized with the Prefect API, based on upstream step definitions in utility.py.

What Changed

• Extended API pull step models and union mapping to include:
  • prefect.deployments.steps.run_shell_script
  • prefect.deployments.steps.pip_install_requirements
• Updated deployment resource pull_steps schema to support new fields, including:
  • script, env, stream_output, expand_env_vars, requirements_file, and shared directory
• Added Terraform ↔ API mapping logic for both new step types.
• Kept deployment datasource pull_steps schema in parity with resource changes.
• Expanded deployment acceptance test fixture coverage to include both new pull step types.
• Regenerated deployment docs for resource and datasource nested pull_steps schema.

Validation

• Formatted updated Go files with gofmt.
• Ran targeted package compile/test checks for touched areas (internal/api, deployment resource, deployment datasource).

Closes #654

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General

• The contributing guide has been read
• Title follows the conventional commits format
• Body includes Closes <issue>, if available
• Relevant labels have been added
• Draft status is used until ready for review

Code-level changes

• Unit tests are added/updated
• Acceptance tests are added/updated (including import tests, when needed)

New or updated resource/datasource

• Documentation is added (generated by mise run docs from source code)
  - When applicable, provide a link back to the relevant page in the Prefect documentation site.
  - Use the doc preview tool to confirm page(s) render correctly.
• For resources, the following are added:
  - Resource example under examples/resources/prefect_<name>/resource.tf
  - Import example under examples/resources/prefect_<name>/import.sh
• For datasources, the following is added:
  - Datasource example under examples/data-sources,resources>/prefect_<name>/data-source.tf

[mitchnielsen]

Thanks for opening this @bdalpe. Looks like there are some test failures to check out.

[bdalpe]

Thanks @mitchnielsen. Lint issues should be fixed now.

[mitchnielsen]

@bdalpe what do you think of adding example(s) in the deployment example? I think it could be helpful for end users to see a real example of how you'd set this up.

[bdalpe]

@mitchnielsen good call out. I added the missing supported steps to the example resource file.