Move prepareClientToWrite out of loop for HGETALL command

[imasahiro]

Similar to #860 but this is for HGETALL families (HGETALL/HKEYS/HVALS). This patch moves prepareClientToWrite out of the loop to reduce the function overhead.

• Test Environment
  • OS: Rocky Linux release 9.4
  • Kernel: 5.14.0-427.22.1.el9_4.x86_64
  • CPU: Intel(R) Xeon(R) Silver 4210
  • Server and Client at different host/vm
• Test script

# Load generator side
for i in `seq 1 500`; do
    ./valkey-cli -h $H -p $P hset h500 "k$i" "v$i" > /dev/null
done
./valkey-benchmark -h $H -p $P --csv -d 100 -r 1000000 -n 1000000 -c 50 --threads 4 HGETALL h500

$ cat tmp.conf
bind * -::*
daemonize no
protected-mode no
save ""

./src/valkey-server ./tmp.conf

test	unstable(150c197) rpc	this patch (rpc)	improvements
HGETALL h1	85084.66	86926.29	2.16446772
HGETALL h10	78400.62	76893.5	-1.922331737
HGETALL h25	64487.01	58802.77	-8.814550403
HGETALL h50	47587.32	49360.78	3.726749058
HGETALL h100	33028.37	34454.25	4.317137055
HGETALL h300	14628.22	15540.98	6.239720212
HGETALL h500	9593.52	10395.44	8.358975642

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.50%. Comparing base (b5eb793) to head (533f4a0).
Report is 9 commits behind head on unstable.

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable    #1119      +/-   ##
============================================
- Coverage     70.60%   70.50%   -0.11%     
============================================
  Files           114      114              
  Lines         61717    61734      +17     
============================================
- Hits          43578    43526      -52     
- Misses        18139    18208      +69     

Files with missing lines	Coverage Δ
src/networking.c	88.07% <100.00%> (-0.37%)	⬇️
src/server.h	100.00% <ø> (ø)
src/t_hash.c	95.88% <100.00%> (+0.03%)	⬆️

... and 14 files with indirect coverage changes