Revert to original SFT build settings

Leveled is always CPU bound during tests, and it is the merge in the
ledger that drains the CPU hardest,

src/leveled_sft.erl

@@ -179,7 +179,7 @@
 -define(DWORD_SIZE, 8).
 -define(CURRENT_VERSION, {0,1}).
 -define(SLOT_COUNT, 256).
--define(SLOT_GROUPWRITE_COUNT, 64).
+-define(SLOT_GROUPWRITE_COUNT, 32).
 -define(BLOCK_SIZE, 32).
 -define(BLOCK_COUNT, 4).
 -define(FOOTERPOS_HEADERPOS, 2).
@@ -189,7 +189,7 @@
 -define(COMPRESSION_LEVEL, 1).
 -define(HEADER_LEN, 56).
 -define(ITERATOR_SCANWIDTH, 1).
--define(MERGE_SCANWIDTH, 32).
+-define(MERGE_SCANWIDTH, 16).
 -define(BLOOM_WIDTH, 48).
 -define(DELETE_TIMEOUT, 10000).
 -define(MAX_KEYS, ?SLOT_COUNT * ?BLOCK_COUNT * ?BLOCK_SIZE).