Edit showFoldingControls to have a never setting

[jzyrobert]

This PR fixes #58708

Demo:

vcxsrv_CBxfgCEEuk.mp4

• Add 'never' as a setting with a description to both editor.showFoldingControls and notebook.showFoldingControls
• Ensure lineDecorationWidth is updated with the setting
• Don't show visible folding decorations when set to never

Of consideration:

• Should the setting actually remove the folding decorations instead of using the hidden one? Does anything depend on the decorations assumed to be there?
• I edited commentsEditorContribution for the gutter size but I don't actually know what this does/how to open this "comment editor"
• What kind of tests could be added for this?

[aeschli]

Great job!

We still need the decoration to track the updated ranges.
I also tested the editor with comments.

Adding @rebornix for reviewing the notebook changes

[rebornix]

Looks great!