Allow extensions to determine if a position is within a fold. #22276
Description
This is currently the most demanded features of VSCodeVim: VSCodeVim/Vim#1004
The main problem with Folds and Vim is that some motions will skip right over folded areas (like moving up/down). We need to know if we are in a folded area so we can iterate these motions until we are out of the fold.
An API like vscode.window.activeTextEditor.getAllFoldedRegions(): vscode.Range[] would be ideal.
An API like vscode.window.activeTextEditor.isPositionInFold(position: vscode.Position): boolean would also be great.