fix: remove the auth_zones lock and count up/down queries in a common way

[sakateka]

The lock field in the auth_zones struct is used only to protect the up/down query counters. My understanding is that the auth_zones struct is only constructed when there are no other threads, so there are no possibilities for concurrent access. However, concurrent modifications still occur in auth_zones.c, specifically during query counting. By adopting a common approach to tracking up/down queries, similar to that used for other server statistics, we can simplify the codebase and eliminate the need for locking mechanisms.

I benchmarked the performance of this patch using the following configuration to effectively disable cache:

...
msg-cache-size: 2b
msg-cache-slabs: 1
rrset-cache-size: 2b
rrset-cache-slabs: 1
key-cache-size: 2b
key-cache-slabs: 1
neg-cache-size: 2b
...

Results:
Before

Read 9M.qerires, got 9000000 queries
qps: 137430
...
qps: 137043
overall time: 15.0001 sec
0(NOERROR): 2070494 replies
average qps: 138032

After

Read 9M.qerires, got 9000000 queries
qps: 159759
qps: 161599
...
qps: 166993
qps: 157685
overall time: 15 sec
0(NOERROR): 2451661 replies
average qps: 163444

[sakateka]

This patch can be implemented without removing the auth_zones lock.
If there is any doubt about removing this lock, I can return it.
But as far as I can see, this lock is not used anywhere in the current code to protect ztree for writing.

[sakateka]

If you don't like big lock removal, I create another PR that reworks counters but doesn't touch auth_zones' lock.
#1169

[sakateka]

Closed in favor of #1169