Motivation:
  - When strings are encoded with `.encode("UTF-16LE")` `.blank?` throws
  an `Encoding::CompatibilityError` exception.
  - We tested multiple implementation to see what the fastest
  implementation was, rescueing the execption seems to be the fastest
  option we could find.

Related Issues:
  - #28953

Changes:
  - Add a rescue to catch the exception.
  - Added a `Concurrent::Map` to store a cache of encoded regex objects
  for requested encoding types.
  - Use the new `Concurrent::Map` cache to return the correct regex for
  the string being checked.