Function _regexp_replace_static_pattern_replace 

fn _regexp_replace_static_pattern_replace<T: OffsetSizeTrait>(
    args: &[ArrayRef],
) -> Result<ArrayRef>

Special cased regex_replace implementation for the scenario where the pattern, replacement and flags are static (arrays that are derived from scalars). This means we can skip regex caching system and basically hold a single Regex object for the replace operation. This also speeds up the pre-processing time of the replacement string, since it only needs to processed once.