Expose redpanda global 'Dot' context publicly

[andrewstucki]

Exposing a Dot method so that we can do roughly the following:

1. Initialize a Dot instance with some given PartialValues/release version.
2. Call into the individual object construction helpers (i.e. ServiceInternal) to generate a Kubernetes object with filled-in user-specified values + defaults
3. Use those rendered objects to do things like construct connection parameters for a cluster.