The current code evaluates our custom packages once for each node, which adds
signifcant amount of time to evaluate a grid. We can reduce this, by adding the
custom package set as an attribute to the nixpkgs set we pass to morph.

This doesn't change how we refer to those packages, as we continue to expose the
custom package set as a module attribute.

These are the times to evaluate all three grids (on a partially loaded system),
when there was nothing new to build:

```
before:
real	2m27.837s
user	3m35.528s
sys	0m3.722s

after:
real	1m12.748s
user	1m34.047s
sys	0m3.346s
```

Fix Grafana start on local dev after upgrade to NixOS 21.11

See merge request !241

Grafana 8 on NixOS 21.11 fails harder than 7.x on 21.05 when its
`grafana-admin.password` file is missing.  Provide it regardless
whether Google auth is configured or not.

Minor factoring improvements to the tests

Closes #104

See merge request !239

Fix up local dev VM grid IPs to be in line with MR !232

See merge request !240

Update nixos to 21.11

See merge request !222

This also update ZKAPAuthorizer to a python3 using version.

This is disallowed in nixos 21.11 as it is a potential security issue.

Update nixpkgs.

See merge request !238

Collect some monitoring host details automatically.

See merge request !234

update to the new host key

See merge request !235

Fix megacli2prom out-of-range error

See merge request !229

bump to the ZKAPAuthorizer branch that pulls in and is compat w/ the new Tahoe-LAFS

Closes #98

See merge request !230

Update nixpkgs.

See merge request !231

Merge most of the code from the `customize-*.nix` nodes into the base modules.

See merge request !233

move all of the hosts from 192.168.67.x to 192.168.56.x

Closes #101

See merge request !232

The VirtualBox documentation says this is the network to use for host-only
networking.

Take what I learned from @tomprince in
https://whetstone.privatestorage.io/privatestorage/PrivateStorageio/-/merge_requests/220#note_17605 :
Assigning a service a `startAt' will make timer.target start it,
no need to also have it `wantedBy' multiuser.target.

Also add megacli2prom to the path even if it should be already because
of megacli2prom.  Better be safe than sorry.

use a different state directory for the issuer's voucher database

Closes privatestorageops#399

See merge request !226