refactor: migrate ingress definition out of beta (#679)

### Description of the change

Redesigned ingress configuration to align better with implicit best practices.

### Benefits

- Smarter defaults
- More tests
- Remove [deprecated API Versions](extensions/v1beta1) (e.g. `extensions/v1beta1`) and always use `networking.k8s.io/v1`

### Possible drawbacks

Hopefully 🙃 none

### Applicable issues

fix #674

### Additional information

- Define `ingress.annotations` via helpers
- Move tests from `tests/deployment` to `tests/ingress`
- Use own tests file for ingress tpl tests
- Ensure defaults of `path` and `pathType` are always rendered
- Set top-level default value for `ingress. pathType`
- Change default of `ingress.hosts[0].paths` to `[]` to ensure proper rendering via template

### ⚠ BREAKING

I think all of these changes should be backward comp with existing ingress definitions, but surely worth highlighting in the changelog of the release.

### Checklist

<!-- [Place an '[X]' (no spaces) in all applicable fields. Please remove unrelated fields.] -->

- [x] Parameters are documented in the `values.yaml` and added to the `README.md` using [readme-generator-for-helm](https://github.com/bitnami-labs/readme-generator-for-helm)
- [x] Breaking changes are documented in the `README.md`
- [x] Templating unittests are added

Co-authored-by: justusbunsi <justusbunsi@noreply.gitea.com>
Co-authored-by: justusbunsi <sk.bunsenbrenner@gmail.com>
Reviewed-on: https://gitea.com/gitea/helm-gitea/pulls/679
Co-authored-by: pat-s <patrick.schratz@gmail.com>
Co-committed-by: pat-s <patrick.schratz@gmail.com>

values.yaml

@@ -157,33 +157,25 @@ service:
 
 ## @section Ingress
 ## @param ingress.enabled Enable ingress
-## @param ingress.className Ingress class name
+## @param ingress.className DEPRECATED: Ingress class name
+## @param ingress.pathType Ingress Path Type
 ## @param ingress.annotations Ingress annotations
 ## @param ingress.hosts[0].host Default Ingress host
 ## @param ingress.hosts[0].paths[0].path Default Ingress path
-## @param ingress.hosts[0].paths[0].pathType Ingress path type
 ## @param ingress.tls Ingress tls settings
-## @extra ingress.apiVersion Specify APIVersion of ingress object. Mostly would only be used for argocd.
 ingress:
   enabled: false
-  # className: nginx
-  className:
-  annotations:
-    {}
-    # kubernetes.io/ingress.class: nginx
-    # kubernetes.io/tls-acme: "true"
+  className: ""
+  pathType: Prefix
+  annotations: {}
   hosts:
     - host: git.example.com
       paths:
         - path: /
-          pathType: Prefix
   tls: []
   #  - secretName: chart-example-tls
   #    hosts:
   #      - git.example.com
-  # Mostly for argocd or any other CI that uses `helm template | kubectl apply` or similar
-  # If helm doesn't correctly detect your ingress API version you can set it here.
-  # apiVersion: networking.k8s.io/v1
 
 ## @section deployment
 #