gdb/workqueue: add basic workqueue dump support

[XuNeo]

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Summary

(gdb) worker
hpwork@0x40424b40, idle, 2 threads, 0 work
lpwork@0x40424a80, idle, 2 threads, 0 work
test@0x4045a8c0, running, 2 threads, 2 work
    Running:
    kworker_s@0x4045a908 work_s@0x406cf330: 0x0 arg=0x406cf300
    Queued:
    work_s@0x406cf370: 0x402f1954 <count_worker> arg=0x406cf318
    work_s@0x406cf3b0: 0x402f1954 <count_worker> arg=0x406cf318
(gdb)

Impact

New tool.

Testing

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