Move "Logging" feature into GitLab Core
This is an implementation issue to move our logging within the Monitor stage into Core
This should have a separate MR to update our documentation as well.
Items with the same "MR breakdown" probably should be solved in the same MR.
## Checklist
| MR breakdown | location | destination | what to move |
| -------- | -------- | ----------- | ------------ |
| `1` | /ee/app/models/ee/clusters/platforms/kubernetes.rb | app/models/clusters/platforms/kubernetes.rb | gitlab~2492649 `read_pod_logs` and other dependencies [see code](https://gitlab.com/gitlab-org/gitlab/blob/28e7f283d85fe2f4097d6c366004be2fd35ab66a/ee/app/models/ee/clusters/platforms/kubernetes.rb#L32)
| `2` | /ee/config/routes/project.rb | /config/routes/project.rb | gitlab~2492649 `resources :logs` path [see code](https://gitlab.com/gitlab-org/gitlab/blob/master/ee/config/routes/project.rb#L67) |
| `2` | /ee/lib/ee/gitlab/etag_caching/router.rb | ee/lib/ee/gitlab/etag_caching/router.rb | gitlab~2492649 route etag caching regex [see code](https://gitlab.com/gitlab-org/gitlab/blob/28e7f283d85fe2f4097d6c366004be2fd35ab66a/ee/lib/ee/gitlab/etag_caching/router.rb#L12)
| `2` | ee/app/serializers/ee/environment_entity.rb | - | gitlab~2492649 `project_path` and `enable_advanced_logs_querying` (if still needed after refactoring) |
| `3` | /ee/app/services/pod_logs_service.rb | /app/services/pod_logs_service.rb | gitlab~2492649 service + specs |
| `3` | /ee/app/controllers/projects/logs_controller.rb | /app/controllers/projects/logs_controller.rb | gitlab~2492649 controller + specs |
| `4` | /ee/app/assets/javascripts/logs | /app/assets/javascripts/logs | gitlab~3412464 entire vue dir |
| `4` | /ee/spec/frontend/logs | /spec/frontend/logs | gitlab~3412464 entire specs dir |
| `4` | /ee/app/views/projects/logs/ | /spec/frontend/logs | gitlab~3412464 entire haml dir |
| `5` | /doc/user/project/clusters/index.md | - | gitlab~2278655 [ultimate tag](https://gitlab.com/gitlab-org/gitlab/blob/28e7f283d85fe2f4097d6c366004be2fd35ab66a/doc/user/project/clusters/index.md#L51) |
| `5` | /doc/user/project/clusters/kubernetes_pod_logs.md | - | gitlab~2278655 [ultimate tag](https://gitlab.com/gitlab-org/gitlab/blob/28e7f283d85fe2f4097d6c366004be2fd35ab66a/doc/user/project/clusters/kubernetes_pod_logs.md#L1) |
## Technical Requirements
- We should refactor logs according to https://gitlab.com/gitlab-org/gitlab/issues/39092 in order to avoid conflicts when moving to core.
epic