When we set a gateway outside a subnet in Linux, this fails with:
```
ip-route-add-default: netlink response indicates error, rc = -101
```
To resolve the error, we should first add a route to the gateway outside
the subnet, which this PR does.
- Bindable is generally useful, so it makes sense to move it out of the
netlink library. Removed Equatable conformance from Bindable as this
isn't generally necessary (it's only used for unit tests in netlink).
- Fix some offset checks in a couple data binding functions and improve
the unit tests.
Adds support for grabbing stats for an iface. This will be surfaced in a
coming change to get container level statistics from the guest, where
one field will be network stats.
This change adds documentation to quite a few existing public types that
didn't have a blurb before.
Additionally, this fixes a couple things that I think either didn't make
sense when going to document them:
- Rename ConnectionStream to VsockConnectionStream. This type only
functions for vsock connections.
- Deletes NsLock+Closure. This was not used anywhere.
- Rename ContainerizationOCI/Config.swift to ImageConfig.swift.
Signed-off-by: Danny Canter <danny_canter@apple.com>