Eliminate hashTypeIterator memory allocation by assigning it on stack

[imasahiro]

At redis/redis#11245, we provided dict iterator API to initialize/release the iterators without memory allocation. This change is for hash iterator.

The memory (de)allocation consumes 2.4% of cpu resource when we execute HGETALL command.

For big hashtable, the impact of this change is smaller but for small hashtable, it sometimes has a positive impact

test	unstable(ac569c0) rpc	this patch (rpc)	improvements
HGETALL h1	78192.2	79802.09	2.058888227
HGETALL h10	75075.08	74850.3	-0.29940694
HGETALL h25	68634.18	69541.03	1.321280447
HGETALL h50	60639.14	59548.62	-1.798376428

for i in `seq 1 1`; do
    ./valkey-cli -h $H -p $P hset h1 "k$i" "v$i" > /dev/null
done
for i in `seq 1 10`; do
    ./valkey-cli -h $H -p $P hset h10 "k$i" "v$i" > /dev/null
done
for i in `seq 1 25`; do
    ./valkey-cli -h $H -p $P hset h25 "k$i" "v$i" > /dev/null
done
for i in `seq 1 50`; do
    ./valkey-cli -h $H -p $P hset h50 "k$i" "v$i" > /dev/null
done
./valkey-benchmark --csv -n 1000000 -r 1000000 -h $H -p $P HGETALL h1
./valkey-benchmark --csv -n 1000000 -r 1000000 -h $H -p $P HGETALL h10
./valkey-benchmark --csv -n 1000000 -r 1000000 -h $H -p $P HGETALL h25
./valkey-benchmark --csv -n 1000000 -r 1000000 -h $H -p $P HGETALL h50

[codecov]

Codecov Report

Attention: Patch coverage is 92.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 70.61%. Comparing base (ac569c0) to head (a319d43).
Report is 17 commits behind head on unstable.

Files with missing lines	Patch %	Lines
src/aof.c	71.42%	2 Missing ⚠️
src/t_hash.c	94.59%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable    #1105      +/-   ##
============================================
+ Coverage     70.57%   70.61%   +0.04%     
============================================
  Files           114      114              
  Lines         61695    61711      +16     
============================================
+ Hits          43544    43580      +36     
+ Misses        18151    18131      -20     

Files with missing lines	Coverage Δ
src/debug.c	53.71% <100.00%> (+0.04%)	⬆️
src/server.h	100.00% <ø> (ø)
src/aof.c	80.08% <71.42%> (ø)
src/t_hash.c	95.85% <94.59%> (-0.01%)	⬇️

... and 17 files with indirect coverage changes

[zuiderkwast]

Good idea!

[zuiderkwast]

LGTM