DataGrid: Expose public info about DetailRow being expanded

[tesar-tech]

Description

Closes #5947

This update exposes DataGridRowInfo.DetailRowExpanded, requiring several adjustments:

• Renamed the original DataGridRowInfo:
  Changed to _DataGridRowInfo to reflect its private nature while retaining DataGridRowInfo as the publicly exposed name. Alternatives considered include RowInfo, DataGridRowInfoPublic, etc.

• Introduced a new public DataGridRowInfo:
  This class now directly exposes DetailRowExpanded. And can be used in a future to expose more a different info.

• Renamed HasDetailRow to DetailRowExpanded:
  As mentioned in the issue description. An alternative like DetailRowVisible is possible, given the existing DetailRowStartsVisible, but Expanded feels better. It might also be worth renaming DetailRowStartsVisible to DetailRowStartsExpanded for consistency..

• Renamed GetRowInfo to GetRowInfoPrivate:
  This change allows GetRowInfo to be used as the public method.

Merged 1.7, as it required a sample and a functional gh action for testing.

[stsrki]

I think something is not right with the PR. Too many files is changed. Have you used the wrong target branch?

[tesar-tech]

I think something is not right with the PR. Too many files is changed. Have you used the wrong target branch?

That's because I merged the 1.7 to this branch, because I needed the code example.

If you merge 1.7 to master the extra code won't be part of this pr anymore.

[stsrki]

• As mentioned in the issue description. An alternative like DetailRowVisible is possible, given the existing DetailRowStartsVisible, but Expanded feels better.

🤔DetailRowVisible is not a bad name.