add --dry-run flag to prefect deploy

[zzstoatzz]

closes #17814

problem

When deploying multiple flows with prefect deploy --all, configuration errors could leave deployments in a "half new, half old" state. Users needed a way to validate deployment configurations before making any changes.

solution

Added a --dry-run flag that validates deployment configurations without making any API calls or resource changes.

usage

# Validate single deployment
prefect deploy my_flow.py:my_function --dry-run

# Validate all deployments in project  
prefect deploy --all --dry-run

# Validate specific deployments
prefect deploy -n deployment1 -n deployment2 --dry-run

notes

It's pretty unfortunate how much branching this adds, but without fully refactoring this file, it wasn't clear to me how else to do it.

[codspeed-hq]

CodSpeed Performance Report

Merging #18159 will not alter performance

_{Comparing dry-run (2063c38) with main (8dce080)}

Summary

✅ 2 untouched benchmarks

[github-actions]

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[github-actions]

This pull request was closed because it has been stale for 14 days with no activity. If this pull request is important or you have more to add feel free to re-open it.