migration: Add support for a variable-length array of UINT32 pointers

migration: Add support for a variable-length array of UINT32 pointers

Add support for defining a vmstate field which is a variable-length array
of pointers, and use this to define a VMSTATE_TIMER_PTR_VARRAY() which allows
a variable-length array of QEMUTimer* to be used by devices.

Message-id: 20250909-timers-v1-0-7ee18a9d8f4b@linux.alibaba.com
Reviewed-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: TANG Tiancheng <lyndra@linux.alibaba.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20250911-timers-v3-2-60508f640050@linux.alibaba.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>