Fix LPOS rank passing LLONG_MIN overflow issue

[enjoy-binbin]

There is a minor overflow issue in RANK negation, passing LLONG_MIN
will overflow and is effectively be the same as passing -1.

This is the example before the fix:

127.0.0.1:6666> flushall
OK
127.0.0.1:6666> lpos mylist foo rank -9223372036854775808
(nil)
127.0.0.1:6666> lpush mylist foo foo foo foo foo
(integer) 5

127.0.0.1:6666> lpos mylist foo rank -1
(integer) 4
127.0.0.1:6666> lpos mylist foo rank -5
(integer) 0
127.0.0.1:6666> lpos mylist foo rank -6
(nil)
127.0.0.1:6666> lpos mylist foo rank -9223372036854775807
(nil)

-- this should return nil but it returned the last one because the overflow rank became -1
127.0.0.1:6666> lpos mylist foo rank -9223372036854775808
(integer) 4

Now we limit RANK to not be LLONG_MIN and will throw an error directly
(this is the behavior of Redis 7.2, but with different error words):

127.0.0.1:6666> lpos mylist foo rank -9223372036854775808
(error) ERR rank would overflow

127.0.0.1:6379> lpos mylist foo rank -9223372036854775808
(error) ERR value is out of range, value must between -9223372036854775807 and 9223372036854775807

Unrelated change: a small cleanup, return RedisParseErr instead of
RedisExecErr in Parse.

[JoverZhang]

Thank you.