Move command to export Project contents to Command Palette

[isc-bsaviano]

This PR fixes #1706. The existing Project content export command has been removed from the Projects Explorer and has been replaced with a new command Export Project Contents from Server... which can be found in the Command Palette.

[isc-klu]

We could replace L203–220 with the snippet below. That would remove the need for the temporary const files variable and simplify the logic a bit—what do you think?

    let files: vscode.QuickPickItem[] = (
      await api.actionQuery("SELECT Name FROM %Library.RoutineMgr_StudioOpenDialog(?,?,?,?,?,?,?,?,?,?)", [
        "*",
        "1",
        "1",
        api.ns == "%SYS" ? "1" : "0",
        "1",
        "0",
        generated ? "1" : "0",
        filters.join(" AND "),
        "0",
        mapped ? "1" : "0",
      ])
    ).result.content.map(({ Name: label }) => ({ label, picked: true }));
    if (!files.length) return;