boot.tmpSize option to adjust tmpfs size at /tmp

@CMCDragonkai
@CMCDragonkai You should be able to redefine the tmp.mount unit using the modules/boot/tmp.nix as a reference, just leave in 'size=${config.boot.tmpSize}' if still want to use use the size option.

I'm not sure what would happen if you defined your own tmp.mount and enabled the TmpOnTpmfs option.

The upstream systemd unit had strictatime, so I figured I'd do the same. I think making another option would be more on the side of clutter though.