Api refactoring

[relu]

This is an attempt to bring the api and controller logic closer to what
the other controller components already have set as patterns.

1. Adopt the k8s standard Condition type.
2. Rename ScanInterval to Interval to be consistent with the
   Interval attribute other Spec types have defined, translating to
   reconciliation interval. This attribute is now required.
3. Add ScanTime attribute to the ScanResult type, enabling keeping
   track of the last successful scan execution. Use this value for scan
   frequency throttling.
4. Add optional Timeout attribute to allow custom scan timeout
   handling. The default value is equal to that of the Interval attr.

What is to be debated:

I proposed a different means of handling the reconciliation interval, while previously this was an optional value, it is not required. I think setting the interval should be a conscious decision made by the user considering the expectation of scan frequency and potential throttling imposed by the registry service provider. With this approach, we could recommend a default value while not imposing any restrictions aside from that of it being more than or equal to 1s, the rest of the logic remains in place.
A potential future design proposed by @squaremo, is to not enforce a mandatory value and rather scan as often as possible if no value is provided, while also providing an attribute that would set an upper bound for throttling purposes (at most frequent).

[stefanprodan]

Rename ScanInterval to Interval to be consistent with the
Interval attribute other Spec types have defined, translating to
reconciliation interval. This attribute is now required.

Nice 👍

[squaremo]

Looks good -- but there's a couple of things to fix up:

• copypasta in a comment (see comment)
• the commit message for the third commit doesn't match what that commit does (it doesn't introduce the standard Condition type, which is done earlier)

[relu]

the commit message for the third commit doesn't match what that commit does (it doesn't introduce the standard Condition type, which is done earlier)

Too much history rewriting :)
I squashed that one into the latest commit now, it should be fine. Thanks.

[squaremo]

All makes sense; thanks @relu 🥬