Can we auto-configure the GitLab Runner chart for self-signed certificates?

The following discussion from !1328 (merged) should be addressed:

• @WarheadsSE started a discussion: (+8 comments)

  🤔 That's odd. We should be able to convince the runner to consume our certificate directly, without issue. We should not need to perform the above "copy pasta" of secret content.

We can cherry-pick d5054faf to automate the process of generating the self-singed certificate chain so it is available for GitLab Runner to consume.