This commit removes the uint64Slice type and performs sorting during
filter construction and ZipMatchAny using sort.Slice. The benchmarks
indicated that this speeds up BuildGCSFilter and ZipMatchAny by 10-12%,
likely to the overhead of needing to resolve the sort.Interface methods.
The benchmarks indicate that this improvement is not present for the
smallest query size in our benchmarks, i.e. 100 elements, but the
reduction is only about 3%. This would indicate the at these small
values, the use of reflection is actually slightly slower than interface
method resolution in total.
In this commit, we decrease the default fp rate to 19, or 1/2^19. We do
this as recent analysis by sipa on the bitcoin dev mailing list has
shown that optimally, we can use a value of 2^19 for the fp rate, while
use n=1.497137*2^P rather than n directly. As a result, we can shrink
the filter size by quite a bit, while still maintaining a sane false
positive value.
This change will reduce the total number of allocations required to
create/store the allocated filter as we’ll now perform a _single_
allocation, rather than one each time the the dynamically size slice
reaches capacity.
