patches default impl for crds filter (#12199)

In CrdsFilter.mask all bits after mask_bits are set to 1:
https://github.com/solana-labs/solana/blob/555252f4/core/src/crds_gossip_pull.rs#L65
However the default implementation, sets both mask and mask_bits to zero
which is inconsistent with CrdsFilter::compute_mask for a mask_bits of
zero.

This commit changes the default implementation by setting mask to
`!0u64` (i.e all bits set to one). As a result, for the default crds
filter, `test_mask` will always return true, whereas previously it was
always returning false.
https://github.com/solana-labs/solana/blob/555252f4/core/src/crds_gossip_pull.rs#L85

This is only used in tests and benchmarks, but causes some benchmarks to
be misleading by short circuiting in this line:
https://github.com/solana-labs/solana/blob/555252f4/core/src/crds_gossip_pull.rs#L429

core/src/crds_gossip_pull.rs

@@ -30,13 +30,23 @@ pub const CRDS_GOSSIP_PULL_MSG_TIMEOUT_MS: u64 = 60000;
 pub const FALSE_RATE: f64 = 0.1f64;
 pub const KEYS: f64 = 8f64;
 
-#[derive(Serialize, Deserialize, Default, Clone, Debug, PartialEq, AbiExample)]
+#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, AbiExample)]
 pub struct CrdsFilter {
     pub filter: Bloom<Hash>,
     mask: u64,
     mask_bits: u32,
 }
 
+impl Default for CrdsFilter {
+    fn default() -> Self {
+        CrdsFilter {
+            filter: Bloom::default(),
+            mask: !0u64,
+            mask_bits: 0u32,
+        }
+    }
+}
+
 impl solana_sdk::sanitize::Sanitize for CrdsFilter {
     fn sanitize(&self) -> std::result::Result<(), solana_sdk::sanitize::SanitizeError> {
         self.filter.sanitize()?;
@@ -565,6 +575,20 @@ mod test {
         }
     }
 
+    #[test]
+    fn test_crds_filter_default() {
+        let filter = CrdsFilter::default();
+        let mask = CrdsFilter::compute_mask(0, filter.mask_bits);
+        assert_eq!(filter.mask, mask);
+        let mut rng = thread_rng();
+        for _ in 0..10 {
+            let mut buf = [0u8; HASH_BYTES];
+            rng.fill(&mut buf);
+            let hash = Hash::new(&buf);
+            assert!(filter.test_mask(&hash));
+        }
+    }
+
     #[test]
     fn test_new_pull_with_stakes() {
         let mut crds = Crds::default();