Fix memory leaks when set and shutdown

[danielealbano]

This PR fixes a couple of memory fixes:

• When the key is passed to the hashtable set, the hashtable code takes ownership of its management as the pointer will be stored in the hashtable to avoid copies, in some cases though, when the key is inlined or when an hashtable value is getting overwritten, the key isn't going to be used and should be, therefore freed.
• When the storage db is freed, the memory allocated for the keys and the storage db entries have to be freed up

The PR includes also:

• some minor style fixes
• some minor speed optimization, it's not necessary to GC the storage db entry index that are getting deleted on every internal loop, it's better to take advantage of the internal timer and run the procedure when it ticks, the tick interval has been reduced to 50ms
• some additional tests

[codecov[bot]]

Codecov Report

Merging #138 (cef76ac) into main (09034fb) will increase coverage by 0.24%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #138      +/-   ##
==========================================
+ Coverage   79.94%   80.19%   +0.24%     
==========================================
  Files          86       86              
  Lines        5127     5144      +17     
==========================================
+ Hits         4099     4125      +26     
+ Misses       1028     1019       -9     

Impacted Files	Coverage Δ
src/worker/worker.c	71.60% <ø> (-0.35%)	:arrow_down:
.../data_structures/hashtable/mcmp/hashtable_op_set.c	100.00% <100.00%> (ø)
...redis/command/network_protocol_redis_command_set.c	73.75% <100.00%> (+0.37%)	:arrow_up:
src/storage/db/storage_db.c	48.18% <100.00%> (+1.48%)	:arrow_up:
src/worker/worker_op.c	100.00% <100.00%> (ø)
...rc/network/protocol/redis/network_protocol_redis.c	80.69% <0.00%> (+4.45%)	:arrow_up:

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