Add a "Collapse All Code Cells" option in Fabric Notebooks

Title: Add a "Collapse All Code Cells" option in Fabric Notebooks

Fabric Notebooks currently allow users to collapse code cells individually. However, in large notebooks, manually collapsing each cell is time-consuming.

Please introduce a "Collapse All Code Cells" command that collapses all code cells in a single action while keeping Markdown cells, especially headings, expanded and visible.

This would improve notebook readability, navigation, and productivity during code reviews, documentation, and presentations. A complementary "Expand All Code Cells" option would also be valuable.