Create an interface for determining the release date of an update

**What I'd like:**
I'd like to programmatically be able to associate an updated Bottlerocket image with the datestamp when it was published.

One possible approach to this would be to query the wave schedule information for an update from the TUF repository. Maybe this could be exposed via `apiclient`, e.g.:

```
$ apiclient update release-data $VERSION
{
"version": "$VERSION",
"waves": {
// etc
},
}
```

**Any alternatives you've considered:**
* Bottlerocket release information is also published to SSM via pubsys. Timestamp information could possibly be made available via SSM parameters for variants.