Text-index does not support multi-token substring search where first and last tokens are partial

We've seen many cases where a user wants to search for a substring in a field with a text index. If all of the tokens in the query are complete words, we can directly use a phrase search:
`SELECT * FROM table WHERE text_match("col", '"substring match query"')`
However, if the first or last token is a partial word (e.g., `"string match que"`), the query will not return any results. Treating the query as regex text-match query does not work either as Pinot only supports regex match on a single token.
To work around the limitation, we can use this a query like this:
`SELECT * FROM table WHERE text_match("col", '/*string/ AND match AND /que*/') AND "col" LIKE "%string match que%"`
But this is very slow and computationally expensive due to the LIKE which is necessary for validating the order of the tokens.