Implement scan command

[danielealbano]

This PR implements the redis SCAN command that operates on the key space and let a client to iterate over all the available keys that were present at the time when the (single) SCAN commands were issued.

The PR includes a code refactoring of the storage_db_op_get_keys operation and updates the KEYS command to use the new interface.

Tests are included in the PR together with some minor style fixes.

[codecov]

Codecov Report

Base: 80.35% // Head: 80.42% // Increases project coverage by +0.06% 🎉

Coverage data is based on head (d14590e) compared to base (00b8b28).
Patch coverage: 91.67% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #211      +/-   ##
==========================================
+ Coverage   80.35%   80.42%   +0.06%     
==========================================
  Files         135      136       +1     
  Lines        8062     8114      +52     
==========================================
+ Hits         6478     6525      +47     
- Misses       1584     1589       +5     

Impacted Files	Coverage Δ
...c/module/redis/command/module_redis_command_scan.c	89.19% <89.19%> (ø)
src/storage/db/storage_db.c	64.69% <94.44%> (+0.64%)	⬆️
.../data_structures/hashtable/mcmp/hashtable_op_rmw.c	98.28% <100.00%> (ø)
...c/module/redis/command/module_redis_command_keys.c	88.89% <100.00%> (+1.39%)	⬆️
src/utils_string.c	58.70% <100.00%> (ø)

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