mgmt-tester: Add a regression test hitting hci_sync bug

mgmt-tester: Add a regression test hitting hci_sync bug

Add a test "Add + Remove Device Nowait - Success" that hits a race
condition in kernel hci_sync.c.  On current kernels this causes

BUG: KASAN: slab-use-after-free in hci_update_passive_scan_sync+0x857/0x1230

due to unsafe iteration of hdev->pend_le_conns (in Linux <= 6.4-rc4).

This seems to hit the race condition also without the added emulator
delay (since the emulator runs in the same thread), but it's better to
add the delay since otherwise it'll depend on timings on kernel side.