Backport to branch(3) : Split schema-loader errors and data-loader errors from CoreError

[feeblefakie]

This is an automated request for a manual backport of the following:

• Original PR: Split schema-loader errors and data-loader errors from CoreError #2805
• Commit to backport: de96782

1. Resolve any conflicts that occur during the cherry-picking process.

git fetch origin &&
git checkout 3-pull-2805 &&
git cherry-pick --no-rerere-autoupdate -m1 de96782039f5360397179261b4b9d5d9b6378638

2. Push the changes.
3. Merge this PR after all checks have passed.

Thank you!