add some verbose debug code

Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@gmail.com>
use table_count function in scripts/function_time.kp

Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@gmail.com>
unify verbose output format

verbose print:
[verbose] ...

Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@gmail.com>
add null check for e.field(N)

N should start from 1.

Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@gmail.com>
add table nil key check

Cannot insert nil key into table.

Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@gmail.com>