Pipeline UX improvement

[gitlawr]

1. Change to pipeline in repo model. we don't store pipeline configs in our server side. Users can change the pipeline configs in the UI. After the modification, they can push and update the pipeline file in the repository directly, or download it and do the push later, e.g. using the git command line. Everytime a build is trigger, the configs in pipeline file in the repository will be used.
2. No need to enable pipeline beforehand in cluster level. users can run pipelines by default in project level.(they can try with sample repos before doing any oauth configurations)
3. Setup a jenkins slave pod on each run and remove it when the execution is finished.
4. Setup a local registry so that users can publish image without pre-confirued registries
5. Move logs out of etcd, store in minio, one instance per project.
6. Pipeline related workloads live in a dedicated namespace of a project(naming p-abc-pipeline)
7. For continuous deployment, we maintain and use a service account and limit its access inside the project.
8. Improve workflow to setup pipelines
9. Provide more user-friendly source code/pipeline status infos.

[bmdepesa]

rancher/rancher:master 8/30

Tested w/ updated pipeline test plan.
Overall the pipeline refactor is functioning correctly.

Two issues outstanding:
#15323 - unable to authenticate w/ another repository after logging out of current repository
#15324 - unable to run modified pipeline configuration without pushing to repository