tests: add a new test for rdev lifetime

tests: add a new test for rdev lifetime

This test add and remove a underlying disk to raid concurretly, verify
that the following problem is fixed:

run mdadm test 23rdev-lifetime at Fri Apr 28 03:25:30 UTC 2023
md: could not open device unknown-block(1,0).
sysfs: cannot create duplicate filename '/devices/virtual/block/md0/md/dev-ram0'
CPU: 26 PID: 10521 Comm: test Not tainted 6.3.0-rc2-00134-g7b3a8828043c #115
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe7/0x180
 dump_stack+0x18/0x30
 sysfs_warn_dup+0xa2/0xd0
 sysfs_create_dir_ns+0x119/0x140
 kobject_add_internal+0x143/0x4d0
 kobject_add_varg+0x35/0x70
 kobject_add+0x64/0xd0
 bind_rdev_to_array+0x254/0x840 [md_mod]
 new_dev_store+0x14d/0x350 [md_mod]
 md_attr_store+0xc1/0x1a0 [md_mod]
 sysfs_kf_write+0x51/0x70
 kernfs_fop_write_iter+0x188/0x270
 vfs_write+0x27e/0x460
 ksys_write+0x85/0x180
 __x64_sys_write+0x21/0x30
 do_syscall_64+0x6c/0xe0
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f26bacf5387
Code: 0d 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 84
RSP: 002b:00007ffe98d79e68 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007f26bacf5387
RDX: 0000000000000004 RSI: 000055bd10282bf0 RDI: 0000000000000001
RBP: 000055bd10282bf0 R08: 000000000000000a R09: 00007f26bad8b4e0
R10: 00007f26bad8b3e0 R11: 0000000000000246 R12: 0000000000000004
R13: 00007f26badc8520 R14: 0000000000000004 R15: 00007f26badc8700
 </TASK>

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Jes Sorensen <jes@trained-monkey.org>