Bring in startup probes to the Health trait

[mertdotcc]

For some applications with long startup times, having the liveness and readiness probes set up to a specific value might be problematic as our application is not necessarily not ready yet, as it is still starting up. Kubernetes recently introduced the Startup Probes so that we can have the ability to temporarily disable the liveness and readiness checks until the startup probe succeeds.

I am aware that there is probably not an urgent need for this (also indicated by the non-existence of other issues regarding the lack of startup probes support) since most Camel-K integrations have super fast startup times; but having recently worked on a couple of integrations with quite decent startup times, I feel like ... why not? Let's add 'em.

Open to discussions, thanks in advance!

[mertdotcc]

@squakez If you agree that this is worth adding to Camel-K, I would like to volunteer and take over this. I might need some help here and there though, as this would be my first contribution to the project (outside of some documentation-related commits). But I have been meaning to start contributing to this project, which I use almost every day; and I feel like this would make a nice entry point for me to get started.

[squakez]

Fantastic! We'll be more than happy to help you getting through it. Typically trait development is a very good way to start contributing at the project as you only focus on a specific aspect of the development. I'm assigning this to you and feel free to ping me through this issue or any PR you'll be submitting in order to help you sort out any problem. Also Apache Mailing list is a good way of communicating and Zulip chat (ping me directly as I may miss some thread otherwise).

[mertdotcc]

Alright! Sounds good, thanks @squakez!