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/test/bloom_tests.cpp

@@ -83,7 +83,7 @@ BOOST_AUTO_TEST_CASE(bloom_create_insert_key)
     CBloomFilter filter(2, 0.001, 0, BLOOM_UPDATE_ALL);
     filter.insert(vchPubKey);
     uint160 hash = pubkey.GetID();
-    filter.insert(std::vector<unsigned char>(hash.begin(), hash.end()));
+    filter.insert(hash);
 
     CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
     stream << filter;