Tests occasionally fail since #12000:
```
*** [err]: query buffer resized correctly when not idle in tests/unit/querybuf.tcl
Expected 0 > 32768 (context: type eval line 11 cmd {assert {$orig_test_client_qbuf > 32768}} proc ::test)
*** [err]: query buffer resized correctly with fat argv in tests/unit/querybuf.tcl
query buffer should not be resized when client idle time smaller than 2s
```
The reason may be because we set hz to 100, querybuf shrinks before we count
client_query_buffer. We avoid this problem by setting pause-cron to 1.
this pr fix two wrongs：
1. When client’s querybuf is pre-allocated for a fat argv, we need to update the
querybuf_peak of the client immediately to completely avoid the unexpected
shrinking of querybuf in the next clientCron (before data arrives to set the peak).
2. the protocol's bulklen does not include `\r\n`, but the allocation and the data we
read does. so in `clientsCronResizeQueryBuffer`, the `resize` or `querybuf_peak`
should add these 2 bytes.
the first bug is likely to hit us on large payloads over slow connections, in which case
transferring the payload can take longer and a cron event will be triggered (specifically
if there are not a lot of clients)
Fix test failure which introduced by #9003.
The following case will occur when querybuf expansion will allocate memory equal to (16*1024)k.
1) make use ```CFLAGS=-DNO_MALLOC_USABLE_SIZE```.
2) ```malloc``` will not allocate more under ```alpine```.
The initialize memory of `querybuf` is `PROTO_IOBUF_LEN(1024*16) * 2` (due to sdsMakeRoomFor being greedy), under `jemalloc`, the allocated memory will be 40k.
This will most likely result in the `querybuf` being resized when call `clientsCronResizeQueryBuffer` unless the client requests it fast enough.
Note that this bug existed even before #7875, since the condition for resizing includes the sds headers (32k+6).
## Changes
1. Use non-greedy sdsMakeRoomFor when allocating the initial query buffer (of 16k).
1. Also use non-greedy allocation when working with BIG_ARG (we won't use that extra space anyway)
2. in case we did use a greedy allocation, read as much as we can into the buffer we got (including internal frag), to reduce system calls.
3. introduce a dedicated constant for the shrinking (same value as before)
3. Add test for querybuf.
4. improve a maxmemory test by ignoring the effect of replica query buffers (can accumulate many ACKs on slow env)
5. improve a maxmemory by disabling slowlog (it will cause slight memory growth on slow env).
