Backport of docs - add service sync annotations and k8s service weight annotation into release/1.14.x

[hc-github-team-consul-core]

Backport

This PR is auto-generated from #18032 to be assessed for backporting due to the inclusion of the label backport/1.14.

🚨

Warning automatic cherry-pick of commits failed. If the first commit failed,
you will see a blank no-op commit below. If at least one commit succeeded, you
will see the cherry-picked commits up to, not including, the commit where
the merge conflict occurred.

The person who merged in the original PR is:
@david-yu
This person should manually cherry-pick the original PR into a new backport PR,
and close this one when the manual backport PR is merged in.

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

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

---

Description

Docs for hashicorp/consul-k8s#2293 and also adding new section for Service Sync in the annotations page.

Testing & Reproduction steps

Links

PR Checklist

• updated test coverage
• external facing docs updated
• appropriate backport labels added
• not a security concern

---

Overview of commits

• e1bf428 - ddf214e - e41bd9c - b9cfc86 - 0ddf013 - 1b0b513 - 29442ad - 5e7ddf5 - f2b6fa7 - 83b84a9 - 56d8173 - 0ab44f0 - 69c99fb - b79e124 - fb14419 - 3b7b2a0

[github-team-consul-core-pr-approver]

Auto approved Consul Bot automated PR