This modifies the server to track the recently confirmed transactions
using a much more efficient APBF instead of an LRU cache which has
significant overhead in addition to having to store the entirety of all
items added to it.
This is acceptable because false positives are acceptable as the goal is
to deduplicate transaction requests which is an ideal case for APBFs.
More concretely, the current LRU cache that stores the recently
confirmed transactions takes around 2.67 MiB per profiling while the new
APBF only takes around 180 KiB, a reduction of around 93%, while
exhibiting roughly the same computational performance.
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