[api] enable DIAG_GET query function into commissioner

This PR adds DIAG_GET query command into the commissioner module, allowing users to query diagnostic TLV (extaddr) from a peer Thread device by setting the device's mesh local address than TLV mask bits flag.

Test:

>> config set pskc 445f2b5ca6f2a93a55ce570a70efeecb
[done]
>> start 192.168.9.2 49154
[done]
>> diag query extaddr
Peer Address: fda1:7966:fc90:d97:0:ff:fe00:bc00
Content: {
    "ExtMacAddr": "6e56946f67040080"
}
[done]

tests/integration/test_cli.sh

@@ -62,7 +62,7 @@ test_execute_diag_command()
 
     start_commissioner "${NON_CCM_CONFIG}"
     petition_commissioner
-    send_command_to_commissioner "diag query extaddr"
+    send_command_to_commissioner "netdiag query extaddr"
     stop_commissioner
 
     stop_daemon