Add button to install ingress on kubernetes service

Description

If you have a Kubernetes cluster, and want to use Auto Deploy or Auto DevOps, you're going to need ingress, ideally with Let's Encrypt. Let's make it easy to configure this by providing a button to install it automatically for you (using Helm).

Proposal

Links / references

• Part of https://gitlab.com/gitlab-org/gitlab-ce/issues/35956

Documentation blurb

Overview

What is it? Why should someone use this feature? What is the underlying (business) problem? How do you use this feature?

Use cases

Who is this for? Provide one or more use cases.

Feature checklist

Make sure these are completed before closing the issue, with a link to the relevant commit.

• Feature assurance
• Documentation
• Added to features.yml

marked this issue as related to #35956

mentioned in issue #35956

mentioned in issue #28916 (moved)

added Deliverable label

assigned to @filipa

@pedro will be back from his honeymoon on October 9th @bikebilly. I will see if he can pick it up then.