helm: Explore adding cert-manager (version >=1.9.0) as a chart dependency

[stephen-fox]

What would you like to be added:

We recently added a helm chart in PR #1013. Unfortunately, cert-manager does not support helm's dependency management feature (see above PR's description for more information on that).

It was announced that cert-manager 1.9.0 (may) support this:

Helm: Adds a new namespace parameter which allows users to
override the namespace in which resources will be created.
This also allows users to set the namespace of the chart when
using cert-manager as a sub chart.
(https://github.com/cert-manager/cert-manager/pull/5141, @andrewgkew)

Refer to the release notes for more information: https://github.com/cert-manager/cert-manager/releases/tag/v1.9.0

Why is this needed:

Instead of documenting cert-manager installation as a prerequisite, we can have helm take care of that for us - making our users' lives easier.

User story covered

As a user, I would prefer that the installation process be automated as much as possible. This helps to avoid making mistakes that introduce instability into my usage of the security-profiles-operator.

ps: Thank you to @tylerauerbeck for pointing out the new chart-manager release that included this change.