Backport

This PR is auto-generated from #1771 to be assessed for backporting due to the inclusion of the label backport/1.0.x.

The below text is copied from the body of the original PR.

Currently, there isn't a way to add a set of labels to every pod (see #759 for example). This PR adds a global values.yaml setting that lets you specify labels to apply to every pod/deployment/daemonset/statefulset/job created by the helm chart. This is in addition to the existing extraLabels config for things like clients and servers.

Changes proposed in this PR:

• Add in global.extraLabels values.yaml setting
• Use that setting to apply extra labels to all pods/deployments/daemonsets/statefulsets/jobs created by the consul-k8s helm chart
• bats tests, I guess

How I've tested this PR:

Added bats tests to cover testing extra labels for all applicable resources

How I expect reviewers to test this PR:

Run the tests, maybe deploy the helm chart locally just to make sure it works

Checklist:

• Tests added
• CHANGELOG entry added

  HashiCorp engineers only, community PRs should not add a changelog entry.
  Entries should use present tense (e.g. Add support for...)