Spider connection string is a comma-separated parameter definitions,
where each definition is of the form "<param_title> <param_value>",
where <param_value> is quote delimited on both ends, with backslashes
acting as an escaping prefix.

The code however treated param title the same way as param value when
assigning, and have nonsensical fields like delim_title_len and
delim_title. We remove these.

We also clean up the spider comment connection string parsing,
including:

- Factoring out some code from the parsing function
- Rewriting the struct `st_spider_param_string_parse`, including
  replacing its messy methods with cleaner ones
- And any necessary changes caused by the above changes