fixed getRelated already fetched relations

[rudiservo]

Hello!

• Type: bug fix | new feature | code quality
• Link to issue: #16409

In raising this pull request, I confirm the following:

• [X] I have read and understood the Contributing Guidelines
• [X] I have checked that another pull request for this purpose does not exist
• [ ] I wrote some tests for this PR
• [ ] I have updated the relevant CHANGELOG
• [ ] I have created a PR for the documentation about this change

Small description of change: GetRelated should reuse already fetched relation inside the model, avoiding more hits to the database. If devs need fresh data they can use Model::refresh and with the PR also ResultSet::refresh.

Thanks