Support Hierarchical Queue on Capacity Plugin

[Rui-Gan]

What would you like to be added:

Description: design and implement hierarchical queue management capabilities on the Capacity plugin, to better align with real-world queue usage scenarios and further improve resource utilization in task scheduling.

Task list:

• Add design doc. Proposal: Hierarchical Queue on Capacity Plugin #3591
• hierarchical queue implementation in this repo. feat: add hierarchical queues for capacity plugin #3743

Mentor(s):
@hwdef