Avoid smgrimmedsync() during index build and add unbuffered IO API

When Who What
2022-08-02 18:54:18 Jacob Champion (jchampion) Closed in commitfest 2022-07 with status: Returned with feedback
2022-03-30 18:49:22 Greg Stark (stark) Closed in commitfest 2022-03 with status: Moved to next CF
2022-03-30 18:49:05 Greg Stark (stark) New status: Waiting on Author
2022-01-10 22:53:51 Melanie Plageman (melanieplageman) Changed authors to Melanie Plageman (melanieplageman)
2022-01-10 22:53:34 Melanie Plageman (melanieplageman) Attached mail thread 20210121203656.tc7kqildbqnyihog@alap3.anarazel.de
2022-01-10 22:53:33 Melanie Plageman (melanieplageman) Created patch record