Drop FFMA

[danielealbano]

This PR drops FFMA (Fast-Fixed Memory Allocator), the novel memory allocator implemented for cachegrand, because mimalloc has improved enough to drammatically reduce the impact of the fragmentation as well as allocating and deallocating memory buffer continuously.

To simplify the codebase, as the gap is now minimal, I have decided to remove FFMA and use only one memory allocator instead of two.

[codecov[bot]]

Codecov Report

Attention: 61 lines in your changes are missing coverage. Please review.

Files	Coverage Δ
src/config.c	78.02% <ø> (ø)
src/config_cyaml_schema.c	100.00% <ø> (ø)
...rc/data_structures/hashtable/mcmp/hashtable_data.c	81.48% <ø> (ø)
...a_structures/hashtable/mcmp/hashtable_op_get_key.c	39.47% <ø> (ø)
...tures/hashtable/mcmp/hashtable_op_get_random_key.c	100.00% <ø> (ø)
...data_structures/hashtable/mcmp/hashtable_op_iter.c	93.33% <ø> (ø)
...a_structures/slots_bitmap_spsc/slots_bitmap_spsc.c	95.70% <100.00%> (ø)
...command/helpers/module_redis_command_helper_auth.c	88.89% <ø> (ø)
...command/helpers/module_redis_command_helper_save.c	92.86% <ø> (ø)
...c/module/redis/command/module_redis_command_auth.c	100.00% <ø> (ø)
... and 59 more

... and 5 files with indirect coverage changes

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