bloom: use Span instead of std::vector for insert and contains

We can avoid many unnecessary std::vector allocations by changing
CBloomFilter to take Spans instead of std::vector's for the `insert`
and `contains` operations.

CBloomFilter currently converts types such as CDataStream and uint256
to std::vector on `insert` and `contains`. This is unnecessary because
CDataStreams and uint256 are already std::vectors internally. We just
need a way to point to the right data within those types. Span gives
us this ability.

Signed-off-by: William Casarin <jb55@jb55.com>

src/hash.cpp

@@ -3,6 +3,7 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <hash.h>
+#include <span.h>
 #include <crypto/common.h>
 #include <crypto/hmac_sha512.h>