Revert "Renamed a field"

This reverts commit 8e99d060bd3896ba821faa0cfab5791313bee49d.
Revert "Run current_page eviction in a coro pool, so it's not called recursively."

This reverts commit 0b4c50087302dae5de9c1e62b9f762f06113d407.
Make evicter_t::evict_if_necessary() non-reentrant.