Backport of Added support for go-changelog automations into release/1.0.x

[hc-github-team-consul-core]

Backport

This PR is auto-generated from #1947 to be assessed for backporting due to the inclusion of the label backport/1.0.x.

WARNING automatic cherry-pick of commits failed. Commits will require human attention.

merge conflict error: POST https://api.github.com/repos/hashicorp/consul-k8s/merges: 409 Merge conflict []

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

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I always add details to my commits and there isn't any crossover, so reviewing commit by commit is usually the best way to review my PRs

Changes proposed in this PR:

This PR adds go-changelog support to the Consul-K8s repo. This will be a new way of managing changelog items throughout the release cycle.

• added go-changelog required templates and directories
• added pipeline checks for unintended missing changelogs
  • added a label pr/no-changelog for ignoring missing changelogs if necessary otherwise a changelog is now required
• added contribution instructions for adding changelogs using the go-changelog tool
• modified prepare-release to automatically run go-changelog and add the changes to the CHANGELOG.MD file

How I've tested this PR:

1. Verified that pipeline fails when missing a changelog file

2. Temporarily commited a changelog file with a combination of feature and bug entries, verified pipeline now passes:

3. Ran the following with with LAST_RELEASE_GIT_TAG being set to v1.0.4 and it generated a valid changelog:

 $ changelog-build -last-release ${LAST_RELEASE_GIT_TAG} -entries-dir .changelog/ -changelog-template .changelog/changelog.tmpl -note-template .changelog/note.tmpl -this-release $(git rev-parse HEAD)

FEATURES:

* cli: Transparent Proxy - Service mesh visualization updates [[GH-1947](https://github.com/hashicorp/consul/issues/1947)]
* control-plane: Transparent Proxy - Service mesh visualization updates [[GH-1947](https://github.com/hashicorp/consul/issues/1947)]
* helm: Transparent Proxy - Service mesh visualization updates [[GH-1947](https://github.com/hashicorp/consul/issues/1947)]

BUG FIXES:

* cli: Transparent Proxy - Service mesh visualization updates [[GH-1947](https://github.com/hashicorp/consul/issues/1947)]
* control-plane: Transparent Proxy - Service mesh visualization updates [[GH-1947](https://github.com/hashicorp/consul/issues/1947)]
* helm: Transparent Proxy - Service mesh visualization updates [[GH-1947](https://github.com/hashicorp/consul/issues/1947)]

4. I ran make prepare-release and confirmed that it adds the changes with the correct version and date to CHANGELOG.MD

How I expect reviewers to test this PR:

👀

Checklist:

• [n/a] Tests added
• [n/a] CHANGELOG entry added

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

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Overview of commits

• 5b7b188 - b8dcada - 9310852 - f52927d

[wilkermichael]

Performed manually