Fix DE functional test workflow to be consistent with publish workflow

[willdavsmith]

Description

• Update Radius DE sync: radius side (https://github.com/azure-octo/deployment-engine/pull/514)

Type of change

• This pull request is a minor refactor, code cleanup, test improvement, or other maintenance task and doesn't change the functionality of Radius (issue link optional).

Contributor checklist

Please verify that the PR meets the following requirements, where applicable:

• An overview of proposed schema changes is included in a linked GitHub issue.
  • Yes
  • Not applicable
• A design document PR is created in the design-notes repository, if new APIs are being introduced.
  • Yes
  • Not applicable
• The design document has been reviewed and approved by Radius maintainers/approvers.
  • Yes
  • Not applicable
• A PR for the samples repository is created, if existing samples are affected by the changes in this PR.
  • Yes
  • Not applicable
• A PR for the documentation repository is created, if the changes in this PR affect the documentation or any user facing updates are made.
  • Yes
  • Not applicable
• A PR for the recipes repository is created, if existing recipes are affected by the changes in this PR.
  • Yes
  • Not applicable

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 50.51%. Comparing base (31bec05) to head (5d7372f).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10963      +/-   ##
==========================================
+ Coverage   50.48%   50.51%   +0.03%     
==========================================
  Files         673      673              
  Lines       42094    42094              
==========================================
+ Hits        21251    21265      +14     
+ Misses      18786    18779       -7     
+ Partials     2057     2050       -7     

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[Copilot]

Pull request overview

This PR updates the deployment engine functional test workflows to align with the publish workflow by using pre-copied images from GHCR instead of copying them during test execution.

Key changes:

• Removed image copying steps from functional test workflows
• Updated environment variable naming from IMAGE_NAME to DEST_IMAGE for consistency
• Added documentation comments explaining the expected client_payload structure

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
.github/workflows/functional-test-noncloud.yaml	Removed DE image copying action and updated variable naming to use DEST_IMAGE
.github/workflows/functional-test-cloud.yaml	Updated variable naming from IMAGE_NAME to DEST_IMAGE and removed image copying step
.github/actions/copy-deployment-engine-image/action.yml	Enhanced comment documentation with multi-line example

[Copilot]

The workflow documentation indicates that src_image is part of the expected client_payload (line 36), but this field is not being consumed anywhere in the workflow after the image copying step was removed. Consider removing src_image from the documentation comment if it's no longer needed, or add validation to ensure the payload structure is as expected.