### Description

The commands available to extract dialog information `dlg.profile_list` and `dlg.list` Are not fast enough to output a large amount of dialogs.

After doing some benchmark the time is spent in in `rpc->struct_add`, `rpc->add etc`, etc. it appears to be slowing down linearly.

### Possible Solutions

I made a quick POC to verify what I can get if I output to file instead and I got blazing fast performance, this is good news since it means that iterating over the hash table etc. is super fast.

https://github.com/jchavanton/kamailio/commit/f28c5a6b6364d79ee35acb5be439e5...

``` dialog: outputing large amount of dialogs to file

Test: 1) injecting 100K dialogs with voip_perf

2) confirmation that we have 100K+ dialogs kamcmd dlg.profile_get_size outbound_call 100879

3) execute the quickly hacked modifications to output to /tmp/dialogs.txt kamctl rpc dlg.profile_list outbound_call

3.1) verify how long it took 2020-03-31T22:28:18.398916476Z 12(31) : dialog [dialog.c:2174]: internal_rpc_profile_print_dlgs(): profile->lock 2020-03-31T22:28:18.554379411Z 12(31) : dialog [dialog.c:2190]: internal_rpc_profile_print_dlgs(): profile->lock release // command took less then 20ms

3.2) verify the content of the output wc /tmp/dialogs.txt 124355 117324 20547037 /tmp/dialogs.txt

Note about the content // not everything is outputed in this quick hack but we can imagine that the impact will be very low. call-id[uV.YzlhIZd1inE8SYDAlzmOLG12tYqVS]from[sip:voip_perf@147.75.65.247]to[sip:12060412757@52.42.112.21]h_entry[6207]h_id[44579]ref[2]contact[sip:voip_perf@147.75.65.247:5072;transport=udp]cseq[19528] ```

### Additional Information

I am thinking about adding commands to output to file in `json` and/or `csv`