Preferred Fit Strategy

The default scheduler includes three score plugins (NodeResourcesLeastAllocated, NodeResourcesMostAllocated and RequestedToCapacityRatio) that implement different strategies for preferred resource allocation. Those plugins are mutually exclusive. This KEP proposes to deprecate those plugins and combine them under one Score plugin, the same one used for filtering (namely NodeResourcesFit), and add a ScoringStrategy parameter to NodeResourcesFit plugin config that allows users to select which exact scoring strategy to run. <!-- This section is incredibly important for producing high-quality, user-focused documentation such as release notes or a development roadmap. It should be possible to collect this information before implementation begins, in order to avoid requiring implementors to split their attention between writing release notes and implementing the feature itself. KEP editors and SIG Docs should help to ensure that the tone and content of the Summary section is useful for a wide audience. A good summary is probably at least a paragraph in length. Both in this section and below, follow the guidelines of the [documentation style guide]. In particular, wrap lines to a reasonable length, to make it easier for reviewers to cite specific portions, and to minimize diff churn on updates. [documentation style guide]: https://github.com/kubernetes/community/blob/master/contributors/guide/style-guide.md -->