fix: Correct digest resolution when the replacementName and replacementVersion options are defined

[ssegato81]

Changes

• getDigestConfig function now keeps the original package name and replacementVersion value
• The function that gets the digest for the docker datasource takes into consideration what type of change is happening and uses the correct docker image name and version when the replacementName/replacementVersion values have been defined.

Context

Closes #20304

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required

How I've tested my work (please select one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository

[github-actions]

Please create a GitHub Discussion before continuing with this PR.

Thank you for your PR, but we need to discuss the requirements and implementation first. This PR will be closed, but you can reopen it after the discussion has been resolved.

Thanks, the Renovate team

[rarkins]

Sorry, but this is not an acceptable approach and needs discussion first

[rarkins]

Types should remain unchanged