Impossible to get values from the last, previous and next row in Expressions

[JaneSjs]

• T25561 - How to get values from the last row in a dynamic matrix question
  https://surveyjs.answerdesk.io/internal/ticket/details/T25561
• T21052 - rowIndex cannot be passed to get matrix row value
  https://surveyjs.answerdesk.io/internal/ticket/details/T21052

In the meantime, it's possible to only reference a row by an index 0, 1, etc., and obtain the current row/panel using the row/panel variable.
Consider enhancing the expression syntax and adding more options.

• -1, -2, etc. - to access the last, the second-to-last row, etc.
• prevRow, nextRow and prevPanel, nextPanel - to access the previous, current and next row or panel.