This reverts commit d7e93cfc.

(cherry picked from commit d341a6c9)

1. A better VDBE caching was implemented for local SQL.
2. Local SQL is called via C API rather then Lua.
3. A new prepare-unprepare fiber added to manage SQL statement
   cache.

add limit to fetch

There's still some raft operations which we can't switch to
compare_and_swap yet unfortunately.