Nested-Grids: grid.save() and grid.load() behaviour  #2171

Subject of the issue

A grid is stored as an object using grid.save() for further use. If the same grid is reloaded with grid.load() and then saved again, the object grows recursively, even if no changes have been made to the grid.
This happens with nested grids and gets worse with nested-nested grids (subGridDynamic=true).

A working example is available here: https://dev4.wdns.at/

This example is based on the original Advanced Nested Grids demo, which has been extended by two textareas - nothing else.
The behavior I described can be understood by multiple save and load attempts and monitoring the content of the textareas.

Your environment

• Version of Gridstack: v7.01, HTML5
• Firefox v108, Chromium (ungoogled) v102

Steps to reproduce

• Visit https://dev4.wdns.at/
• Save / Load the grid multiple times
• Check the grid object (textarea)

Expected behavior

Even with multiple save and load processes, only changes to the grid may be applied