Add functionality to pull OIDC provider CA file

[justapill]

What would you like to be added

Add a pre-install task which gives the option to download a root CA file to all master nodes.

Why is this needed

Currently, a user must download the CA file for their OIDC provider separately. Adding this functionality takes that burden off the user.

I have recently discovered this while setting up OIDC on my cluster with keycloak, which has it's certificate issued from Letsencrypt. Thankfully Letsencypt hosts their root CA on a webserver. - curl https://letsencrypt.org/certs/isrg-root-x2.pem

[justapill]

In hindsight, I've remembered that on Ubuntu for example; root CA's are managed by the apt package ca-certificates. I think this functionality would still be appreciated for root CA's that are not included in that package.