Use the `api_gateway` folder under `treetracker-infrastructure` to deploy the ambassador

* First, please check the current config here to see how do we deploy ambassador, we are using new version of it as described in `k3s/emissary.yaml`, is this the correct direction to go? Or we should still stick with the definition in `treetracerk-infrastructure/api_gateway`
* If answer is yes, let's migrate to the api_gateway folder.

Compare the current deployment configuration in k3s/emissary.yaml with the definition in treetracerk-infrastructure/api_gateway. First determine which Ambassador version and deployment path should be authoritative; done means the decision is documented and, if migration is approved, deployment uses the api_gateway folder.

Written by the indexing model from the issue text.