As rxin suggested in #7298 , we should consider to remove `RDDApi`.

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #7302 from sarutak/remove-rddapi and squashes the following commits:

e495d35 [Kousuke Saruta] Fixed mima
cb7ebb9 [Kousuke Saruta] Removed overriding RDDApi