- Closes#1812.
- The network plugin is the source of truth for the variant, if any,
that applies to the network. Resolving a missing variant configuration
option in the API server can create a situation where the variant the
runtime uses for interface selection is incorrect.
- Adds serial suites trait to tests to see whether it helps current CI
issues.
## Type of Change
- [x] Bug fix
- [ ] New feature
- [ ] Breaking change
- [ ] Documentation update
## Motivation and Context
Fixes a flaw in our interface strategy logic.
## Testing
- [x] Tested locally
- [ ] Added/updated tests
- [ ] Added/updated docs
- Refactor network model types: replace `NetworkState` enum and
phase-based NetworkStatus with a flat `NetworkStatus` struct.
- Simplify API server ↔ plugin protocol: plugin `status()` returns
runtime status only, API server owns configuration.
- `NetworksService` `list()`/`create()` now return `NetworkResource`
directly.
- Remove lifecycle phase checks and state machine guards throughout CLI
and API server.
- `variant` is plugin-specific, it's not a required property. This PR
replaces `NetworkPluginInfo` with a `plugin` name property on
`NetworkConfiguration` and an `options` list similar to that for
volumes.
- Moved `variant` to the option list.
J Logan