Add support in HAProxy / Chef / Config Management for releasing Workspaces HTTP Server on .com
<!--IssueSummary start-->
<details>
<summary>
Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards.
</summary>
- [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=578194)
</details>
<!--IssueSummary end-->
MRs:
**Staging**
- https://ops.gitlab.net/gitlab-com/gl-infra/config-mgmt/-/merge_requests/12503+
- https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/merge_requests/6549+
- https://gitlab.com/gitlab-cookbooks/gitlab-haproxy/-/merge_requests/435+
- https://gitlab.com/gitlab-com/gl-infra/production-engineering/-/issues/27886+
**Production**
- ...
<!-- NOTE: For context on MR heading, see:
https://handbook.gitlab.com/handbook/engineering/devops/dev/create/remote-development/index.html#relationship-of-issues-to-mrs
-->
## Description
Add support in HAProxy / Chef / Config Management for releasing Workspaces HTTP Server on .com as per the conversation in https://gitlab.com/gitlab-com/gl-infra/production-engineering/-/issues/27468#note_2786845164
## Acceptance criteria
- [ ] Workspaces HTTP Server is live on gstg. You should be able to create a workspace on staging and access it from the configured URL.
- [ ] Workspaces HTTP Server is live on gprd. You should be able to create a workspace on staging and access it from the configured URL.
## Implementation plan
For each environment(gstg, gprd), do the following
- [ ] Define a pool for the environment ([ref](https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/blob/master/roles/gstg-base-haproxy-main-config.json#L86-L91))
- [ ] Add an override for the port ([ref](https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/blob/master/roles/gstg-base-haproxy-main-config.json#L141))
- [ ] Add a backend definition in HAProxy ([ref](https://gitlab.com/gitlab-cookbooks/gitlab-haproxy/-/blob/master/templates/default/backends/kas.erb?ref_type=heads))
- [ ] Add to enabled backends ([ref](https://gitlab.com/gitlab-cookbooks/gitlab-haproxy/-/blob/master/attributes/default.rb#L24)) (This should be done on an environment level in `chef-repo` until rolled out to `gprd`)
- [ ] Add a frontend definition in HAProxy ([ref](https://gitlab.com/gitlab-cookbooks/gitlab-haproxy/-/blob/master/templates/default/frontends/kas.erb?ref_type=heads))
- [ ] Add to enabled frontends ([ref](https://gitlab.com/gitlab-cookbooks/gitlab-haproxy/-/blob/master/attributes/default.rb#L18)) (This should be done on an environment level in `chef-repo` until rolled out to `gprd`)
- [ ] Add the `8160` port to the existing load balancer [here](https://ops.gitlab.net/gitlab-com/gl-infra/config-mgmt/-/blob/main/environments/gstg/variables.tf?ref_type=heads#L182)
- [ ] Adds DNS records through `config-mgmt` in Terraform:
- [ ] `*.staging.gitlab.dev`
- [ ] `kas.staging.gitlab.com`
<!-- NOTE: Feel free to expand with more sections and headers as needed -->
<!-- DO NOT TOUCH BELOW -->
issue