Create custom properties for Knative generation

[snowdrop-bot]

Description

Currently, if you want to customize the output generated by Dekorate for Knative, you only have access to the same properties as in the Kubernetes (https://github.com/quarkusio/quarkus/blob/master/docs/src/main/asciidoc/kubernetes.adoc#knative) but with knative prefix.

The thing is that minimal customizations specific to knative service should be provided, the list is in https://knative.dev/docs/serving/spec/knative-api-specification-1.0/#service I know that not all of them should be implemented, but at least some of most used would be interesting to provide it.

Implementation ideas

Implement custom Knative serving attributes to be able to customize the output.

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quarkusio#7788

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$upstream:7788$