engine: Wrong variants for the `regexp_count` (reimplement)

[DanCodedThis]

• regexp_count function appears to be working correctly
• What differs is:
  • Wrong errors
  • Wrong <regex_parameters> variants in this arguments
• Reimplement this function using the utils regexp iterator approach

P.S. This is a low-hanging fruit (since regexp_count itself is working correctly and is alike to Snowflake probably in 90% of the cases)