dump_assignments is a little tricky

Assume my goal is to understand the persistent assignments that are being used by Carthage.

I can find `/root/.carthage/state/persistent_assignments/*.mdb`

I can install lmdb-utils and run `mdb_dump -p /root/.carthage/state/persistent_assignments` and get a dump that's not ideal but at least usable

If someone gives me a hint, and I figure out that I need to add `add_provider(carthage.kvstore.persistent_seed_path, 'seed.yml')` , I can use the `dump_assignments` command to get a yaml dump of the assignments, I think. It writes it to the file and then I have to read the file, which is a bit awkward but OK. But the file has a lot fewer K/V pairs than there are in the mdb file, which makes me suspicious.

```
root@radiosim-vm:~/radio-simulation-engine# mdb_dump -p /root/.carthage/state/persistent_assignments
VERSION=3
format=print
type=btree
mapsize=4294967296
maxreaders=126
db_pagesize=4096
HEADER=END
container_net/v4_pool/assignments:10.20.0.48
radiosim_pod|eth0
container_net/v4_pool/assignments:10.20.0.49
webserver.jeff-sandbox.photon.ac|eth0
container_net/v4_pool/assignments:10.20.0.84
keycloak-pod|eth0
container_net/v4_pool/assignments:10.20.0.96
photon.jeff-sandbox.photon.ac|eth0
container_net/v4_pool/assignments:keycloak-pod|eth0
10.20.0.84
container_net/v4_pool/assignments:photon.jeff-sandbox.photon.ac|eth0
10.20.0.96
container_net/v4_pool/assignments:radiosim_pod|eth0
10.20.0.48
container_net/v4_pool/assignments:webserver.jeff-sandbox.photon.ac|eth0
10.20.0.49
container_net/v4_pool/hints:keycloak-pod|eth0
10.20.0.84
container_net/v4_pool/hints:photon.jeff-sandbox.photon.ac|eth0
10.20.0.96
container_net/v4_pool/hints:radiosim_pod|eth0
10.20.0.48
container_net/v4_pool/hints:webserver.jeff-sandbox.photon.ac|eth0
10.20.0.49
dump:container_net/v4_pool/hints
true
DATA=END
```
```root@radiosim-vm:~/radio-simulation-engine# PYTHONPATH=/carthage /carthage/bin/carthage-runner --config config.yml --keep --start --tasks-verbose --command-verbose dump_assignments
Task Handle Certificates last run for at 2023-05-23T16:57:22.923692
Task make download last run for at 2023-05-23T16:57:26.959704
Task Render config.yml.mako template last run for at 2023-05-23T16:57:26.987705
```
```
root@radiosim-vm:~/radio-simulation-engine# ls
README.md ansible carthage_plugin.yml config.yml container.log design engine radiosim resources sample-carthage-config.yml seed.yml
root@radiosim-vm:~/radio-simulation-engine# cat seed.yml
container_net/v4_pool/hints:
radiosim_pod|eth0: 10.20.0.48
webserver.jeff-sandbox.photon.ac|eth0: 10.20.0.49
```

I suspect that I want !dump_assignments to be able to dump to stdout even if I don't define persistent_seed_path. I might also want to be able to set it in config.yml?