[vscode] support workspace.save(URI) and workspace.saveAs(URI) introduced in 1.86.0

[rschnekenbu]

new API introduced on workspace namespace, save(URI) and saveAs(URI)

see https://github.com/microsoft/vscode/blob/e5447598324c57ac814c150148e7e4c830e0f9ee/src/vscode-dts/vscode.d.ts#L13298