tool: add curl command line option --trace-ids

- added and documented --trace-ids to prepend (after the timestamp)
  the transfer and connection identifiers to each verbose log line
- format is [n-m] with `n` being the transfer id and `m` being the
  connection id. In case there is not valid connection id, print 'x'.
- Log calls with a handle that has no transfer id yet, are written
  without any ids.

Closes #11185

src/tool_listhelp.c

@@ -759,6 +759,9 @@ const struct helptxt helptext[] = {
   {"    --trace-ascii <file>",
    "Like --trace, but without hex output",
    CURLHELP_VERBOSE},
+  {"    --trace-ids",
+   "Add transfer/connection identifiers to trace/verbose output",
+   CURLHELP_VERBOSE},
   {"    --trace-time",
    "Add time stamps to trace/verbose output",
    CURLHELP_VERBOSE},