Refactor assert usage.

We should probably define:

• DBMS_ASSUME: (used in logic code)

#ifndef NDEBUG
#  define DBMS_ASSUME(x) DBMS_ASSERT(x)
#else
#  if __has_builtin(__builtin_assume)
#    define DBMS_ASSUME(x) __builtin_assume((x))
#  elif defined(_MSC_VER)
#    define DBMS_ASSUME(x) __assume((x));
#  elif defined(__GNUC__)
#    define DBMS_ASSUME(x) \
     if (!(x)) \
       __builtin_unreachable();
#  else
#    define DBMS_ASSUME(x) \
     do \
     { \
     } while (0)
#  endif
#endif

• DBMS_ASSERT: (used in test code) debug time assert, release time abort

As what we have encountered in #2194, directly usage of assert may cause subtle warnings and it loses the effect in release build.