Add a canonical script that installs Knative

[tdiesler]

Requirement

Installing Knative serving/eventing is a multistep process. It would help to have a common script that can be executed by users and tests.

[squakez]

A script exists for e2e tests in https://github.com/apache/camel-k/blob/main/.github/actions/kamel-install-knative/install-knative.sh

Mind that any "official" effort we do to guide the user for some installation means maintenance effort, hence, looking after any change that it may happen in the third party installation procedure. I'd personally avoid to do that given the limited resources we have, and instead provide the links to the official procedure. Knative is a third party resource for us.

[lburgazzoli]

Relates to https://github.com/apache/camel-k/issues/5463

[tdiesler]

I suggest to have a setup.sh script in each ./e2e/*/files folder where applicable, which is then referenced from .github\actions

I tested the knative setup like this ...

minikube-delete && minikube-start && make images && kamel install --global

./e2e/knative/files/setup.sh && minikube tunnel

time go test -v -tags=integration ./e2e/knative --run TestKnativePlatformDetection

PASS
ok  	github.com/apache/camel-k/v2/e2e/knative	141.058s
go test -v ./e2e/knative -tags=integration --run TestKnativePlatformDetection  2.64s user 1.25s system 2% cpu 2:25.60 total

[tdiesler]

PR: https://github.com/apache/camel-k/pull/5573

[squakez]

Is this solved by #5573? Can I close or still any leftover?