feat: TLS support for the Thanos web endpoint

[vyzigold]

This PR adds a new "WebTLSConfig" field to the ThanosQuerier Spec, which allows the user to specify secrets containing TLS certificates. The ThanosQuerier object is configured to use these secrets.

The secrets are then watched for changes and a reconciliation is triggered when one of them changes. In order to know if the contents of the TLS related secrets changed, a hash is computed from the contents of the secrets. The computed hash value is added to the querier deployment as an env variable. This means, that when that variable changes, a new querier pod is automatically created, which will use the new content of the secrets. (when the content of the secrets is the same, the old pod stays running).

The ServiceMonitor for monitoring the Querier is also modified to use TLS when TLS is enabled.

The first 2 commits of the PR (which add the WebTLSConfig struct and the TLS prometheus client for testing) are shared with #492

[openshift-ci]

Hi @vyzigold. Thanks for your PR.

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[jan--f]

This looks very nice! I have one small question though.

[jan--f]

/ok-to-test

[jan--f]

Thanks!
/lgtm
/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jan--f, vyzigold

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