Add USE_FTS As query parameter

For Flex Index selection in addition USE INDEX(USING FTS) add use_fts as query parameter.
When this is set to true consider FTS index with out USE INDEX hint.
This allows no query modifications in the applications.

use_fts true

If query doesn't have USE INDEX hint or with in the USE INDEX there is no FTS index then all Fts indexes are considered when use_fts query parameter is set to true