feat(deploy): add spin deploy command

[michelleN]

This is an MVP for the spin deploy command. Given
a bindle server url, hippo server url, and hippo
username/password, this command will create
(1) and push a bindle containing the app to the bindle server
(2) a Hippo App with the name provided in the Spin.toml
(3) a Hippo channel in the Hippo App called "spin-deploy"
and create a post request to register a revision in Hippo.
If an app with the same name already exists, this command will
return an error. If a channel with the name spin-deploy exists,
this will return an error. These errors will be handled more
gracefully with prompts/helpful error messages in subsequent PRs.

This commit it meant to lay the groundwork for the deploy command
so folks can start playing with it and collect opinions.

To play with this command:

1. Use the nomad-local-demo to deploy nomad (+ Consul, Traefik, Vault) and bindle.
2. Clone Hippo and in Infrastructure/Jobs/NomadJob.cs, change the driver setting from "exec" to "raw_exec". Remove the artifact stanza so that Nomad uses your local Spin binary. Be sure to set the bindle url env variable given in the ./run_servers.sh output
3. Start hippo with the nomad scheduler and bindle url.

$ dotnet build
$ dotnet run \
--Scheduler:Driver=nomad \
  --Bindle:Url="${BINDLE_URL}"

4. Create a hippo account. Use these creds in the next step
5. Build the wasm module for an example app and then spin deploy --bindle-server <bindle-url> --hippo-username <username> --hippo-password <password>

[radu-matei]

I deployed the Nomad infra, started Hippo, and got an application up and running!
The only thing not working was routing using the default local domain, but I suspect that's an issue with my setup.

Creating the application, channel, and starting it using Nomad worked for me (with the mention that if running IPv6, both Bindle and the Nomad job definition from Hippo need [] around the IP address — ref fermyon/nomad-local-demo#5).

(I have a few non-blocking comments related to error messages and default addresses).

I think this is in a great spot to be iterated on, LGTM.

[radu-matei]

!