Enhance environment trait to include values from secrets/configmaps

[squakez]

We can enhance the trait to include values taken directly from secret without the need to expose them or to mount as files via mount trait. For example we should have something like kamel run test.yaml -t env.vars=MY_VAR=secret:my-secret/my-value converted in a Pod like:

apiVersion: v1
kind: Pod
...
spec:
  containers:
...
    env:
    - name: MY_VAR
      valueFrom:
        secretKeyRef:
          name: my-secret
          key: my-value

[tdiesler]

sign me on

[tdiesler]

PR: #5639