nixos/docker: load more required kernel modules

This builds on #76487.

br_netfilter
------------

When I first added veth it was suggested I add bridge as well. Without
veth I get the following error message when starting the daemon with
security.lockKernelModules=true:

> Running modprobe bridge br_netfilter failed with message: modprobe: ERROR: could not insert 'br_netfilter': Operation not permitted

Therefore if we're going to add bridge we may as well add br_netfilter
as well.

xt_nat
------

Without xt_nat, docker cannot do dnat with iptables, failing with:

> iptables v1.8.4 (legacy): unknown option \"--to-destination\"\nTry `iptables -h' or 'iptables --help' for more information.\n (exit status 2))

0 files changed, 0 insertions, 0 deletions