Pure DocValue optimization for doris-on-es
Future todo:
Today, for every tuple scan we check if pure_docvalue is enabled, this is not reasonable, should check pure_docvalue enabled for one whole scan outside, I will add this todo in future
Enhance doris on es error message and modify some field data transform error.
For varchar/char type, sometimes elasticsearch user post some not-string value to Elasticsearch Index. because of reading value from _source, we can not process all json type and then just transfer the value to original string representation this may be a tricky, but we can workaround this issue
