[FEATURE] Support Yunikorn as a batch scheduler

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#### What is the outcome that you are trying to reach?

[Apache YuniKorn](https://yunikorn.apache.org/) is an alternative Kubernetes scheduler that provides batch scheduling functionality, including gang scheduling, hierarchical queues and job ordering. The Spark operator should support Yunikorn as a batch scheduler by supplying the necessary task group information on the driver pod annotations.

#### Describe the solution you would like

- [x] Add a Yunikorn scheduler implementation that patches task group annotations and calculates `minResources` https://github.com/kubeflow/spark-operator/pull/2107
- [x] Allow a default batch scheduler to be specified so that all applications can be batch scheduled easily https://github.com/kubeflow/spark-operator/pull/2143
- [ ] Add a gang scheduling end to end test using Yunikorn to prevent future regressions
- [x] Prep work https://github.com/kubeflow/spark-operator/pull/2148
- [x] Add a doc page https://github.com/kubeflow/website/pull/3872

#### Describe alternatives you have considered

#### Additional context

The remaining work is an end-to-end gang-scheduling test using YuniKorn; no source file or test path is named in the issue. Review the linked prep work in PR 2148 and the existing YuniKorn implementation, then add coverage that prevents regressions in gang scheduling.

Written by the indexing model from the issue text.