fixed getRelated already fetched relations

[rudiservo]

Hello!

• Type: bug fix | new feature | code quality
• Link to issue: [BUG]:ORM Model::getRelated not reusing already fetched relations #16409

In raising this pull request, I confirm the following:

• I have read and understood the Contributing Guidelines
• 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