WIP feat: Thanos Querier to Thanos sidecar mTLS

[vyzigold]

This adds mTLS to connections from Thanos Querier to Thanos Sidecar. The connection uses selfsigned certificates generated by code taken from CMO.

The PR is missing functionality for watching the certificate secrets and restarting pods when the secrets change to start using new certificates. My plan is to use similar approach as in this PR if it's accepted by reviewers #496 . (compute a hash of the secret and include them as environment variables in the pods to trigger the restarts). I'll get back to this once the PR I mentioned before merges or a different approach to restarting pods is found.

[openshift-ci]

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[openshift-ci]

Hi @vyzigold. Thanks for your PR.

I'm waiting for a rhobs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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