reference/performance: add hint for INL_HASH_JOIN and INL_MERGE_JOIN (#1868)
reference/performance: add hint for INL_HASH_JOIN and INL_MERGE_JOIN (#1868)

* reference/performance: add hint for INL_HASH_JOIN and INL_MERGE_JOIN

* fix typos

* address comments

Co-Authored-By: Lilian Lee <c684465c17314189c18707959627e2ec4fdec2d0@pingcap.com>

Co-authored-by: Lilian Lee <c684465c17314189c18707959627e2ec4fdec2d0@pingcap.com>
pingcap/docs,pingcap/docs,pingcap/docs