Configurable Scaling Delay with Pod Resource Exposure

<!-- 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. --> This proposal introduces a new option, scale-delay-time, in the CPU Manager static policy. The scale-delay-time option ensures the updated cpuset is not applied sooner than the specified delay after a container scale-down event. This proposal also extends the downward API volume to expose the CPUs assigned to containers. This extension is controlled by the new DownwardAPIAssignedResources feature gate. Together, these two features allow latency-sensitive applications to obtain the assigned cpuset in advance via the downward API. This enables workloads to prepare for CPU removal triggered by scale-down within the guaranteed delay window scale-delay-time. As a result, performance degradation caused by sudden CPU loss is avoided.