Add compatibility test for string expression operators (21 total)

[eerxuan]

core operator expressions string - concat
core operator expressions string - indexOfBytes
core operator expressions string - indexOfCP
core operator expressions string - ltrim
core operator expressions string - regexFind
core operator expressions string - regexFindAll
core operator expressions string - regexMatch
core operator expressions string - replaceAll
core operator expressions string - replaceOne
core operator expressions string - rtrim
core operator expressions string - split
core operator expressions string - strcasecmp
core operator expressions string - strLenBytes
core operator expressions string - strLenCP
core operator expressions string - substr
core operator expressions string - substrBytes
core operator expressions string - substrCP
core operator expressions string - toLower
core operator expressions string - toString
core operator expressions string - toUpper
core operator expressions string - trim