As part of my background investigation on WT-11595, I want to experiment with next-fit allocation in WT. This ticket is a place to do that.

Next fit allocation will remember the last place an allocation happened in a block handle (WT_BLOCK). The next write will start look for a place to allocate starting from that address. I.e., it will use first fit starting from that address. If we reach the end of the file, we cycle back to be beginning and try to allocate from there. If we cycle all the way back to where we started, then we grow the file.

My goal is to look at the result this has on IO patterns and file layout. So the runtime performance of this PoC is of secondary importance.