query-command-line-options outputs def_value_str

QMP command query-command-line-options shows details information of
parameters, since added def_value_str, also output it in the QMP
command.

v16->v17:
1) add "Since 1.6" tag.
2) rename def_str_value to "default".

Signed-off-by: Dong Xu Wang <wdongxu@linux.vnet.ibm.com>
remove QEMUOptionParameter related functions and struct

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Dong Xu Wang <wdongxu@linux.vnet.ibm.com>