Make it possible to install openshift-routes in a different namespace than "cert-manager" using oc process

[maelvls]

This is a continuation of #32. This PR focuses on a very precise request coming from people relying on the oc process command to substitute variables such as $NAMESPACE in the static manifest.

To test this PR, run the following:

oc process -f https://raw.githubusercontent.com/maelvls/openshift-routes/different-namespace/deploy/static/cert-manager-openshift-routes.yaml \
  -p NAMESPACE=<NAMESPACE_NAME> \
  | oc create -f -

[jetstack-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[jetstack-bot]

Thanks for your pull request. Before we can look at it, you'll need to add a 'DCO signoff' to your commits.

📝 Please follow instructions in the contributing guide to update your commits with the DCO

Full details of the Developer Certificate of Origin can be found at developercertificate.org.

The list of commits missing DCO signoff:

• 765e6e0 make it possible to install to a different namespace
• bd7fc5b deploy/static: use '${RELEASED_VERSION}' instead of '$RELEASED_VERSION'
• e7057ab deploy/static: introduce '${NAMESPACE}'
• effea4c deploy/static: use kube-system as the default election namespace

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[jetstack-bot]

PR needs rebase.

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[cert-manager-prow]

@maelvls: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-cert-manager-openshift-routes-smoke	457b447	link	true	/test pull-cert-manager-openshift-routes-smoke

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository. I understand the commands that are listed here.

[maelvls]

Closing as I wasn't able to find the time to finish this. Please feel free to take over!