Equivalent to creating a positional writer, writing bytes, and then flushing.
pub fn writePositionalAll(file: File, io: Io, bytes: []const u8, offset: u64) WritePositionalError!void
pub fn writePositionalAll(file: File, io: Io, bytes: []const u8, offset: u64) WritePositionalError!void {
var index: usize = 0;
while (index < bytes.len)
index += try io.vtable.fileWritePositional(io.userdata, file, &.{}, &.{bytes[index..]}, 1, offset + index);
}