Given a list of deployment steps as strings, write a Python function that validates and executes them in order for a simple web application deployment workflow. Each step is one of: build, test, package, deploy, verify. Return the ordered list of executed steps if the workflow is valid. If a step appears out of order, is duplicated, or an unknown step is present, return [].
Example 1:
Input: steps = ["build", "test", "package", "deploy", "verify"]
Output: ["build", "test", "package", "deploy", "verify"]
Explanation: All deployment stages appear exactly once and in the required order.
Example 2:
Input: steps = ["build", "package", "test", "deploy", "verify"]
Output: []
Explanation: `package` appears before `test`, so the workflow is invalid.
1 <= len(steps) <= 10steps[i] is a non-empty lowercase stringbuild -> test -> package -> deploy -> verify
