Relaxed clippy fixes/nits (#2661)

This PR contains just a few clippy fixes and nits, which are, however,
relaxed by workspace clippy settings here:
https://github.com/paritytech/polkadot-sdk/blob/master/Cargo.toml#L483-L506

---------

Co-authored-by: Dmitry Sinyavin <dmitry.sinyavin@parity.io>
Co-authored-by: ordian <write@reusable.software>
Co-authored-by: command-bot <>
Co-authored-by: Bastian Köcher <git@kchr.de>

substrate/primitives/database/src/lib.rs

@@ -101,7 +101,9 @@ pub trait Database<H: Clone + AsRef<[u8]>>: Send + Sync {
 	/// This may be faster than `get` since it doesn't allocate.
 	/// Use `with_get` helper function if you need `f` to return a value from `f`
 	fn with_get(&self, col: ColumnId, key: &[u8], f: &mut dyn FnMut(&[u8])) {
-		self.get(col, key).map(|v| f(&v));
+		if let Some(v) = self.get(col, key) {
+			f(&v)
+		}
 	}
 
 	/// Check if database supports internal ref counting for state data.

substrate/primitives/runtime-interface/proc-macro/src/utils.rs

@@ -89,7 +89,7 @@ struct RuntimeInterfaceFunctionSet {
 impl RuntimeInterfaceFunctionSet {
 	fn new(version: VersionAttribute, trait_item: &TraitItemFn) -> Result<Self> {
 		Ok(Self {
-			latest_version_to_call: version.is_callable().then(|| version.version),
+			latest_version_to_call: version.is_callable().then_some(version.version),
 			versions: BTreeMap::from([(
 				version.version,
 				RuntimeInterfaceFunction::new(trait_item)?,

substrate/primitives/storage/src/lib.rs

@@ -414,12 +414,13 @@ impl ChildTrieParentKeyId {
 ///
 /// V0 and V1 uses a same trie implementation, but V1 will write external value node in the trie for
 /// value with size at least `TRIE_VALUE_NODE_THRESHOLD`.
-#[derive(Debug, Clone, Copy, Eq, PartialEq)]
+#[derive(Debug, Default, Clone, Copy, Eq, PartialEq)]
 #[cfg_attr(feature = "std", derive(Encode, Decode))]
 pub enum StateVersion {
 	/// Old state version, no value nodes.
 	V0 = 0,
 	/// New state version can use value nodes.
+	#[default]
 	V1 = 1,
 }
 
@@ -432,12 +433,6 @@ impl Display for StateVersion {
 	}
 }
 
-impl Default for StateVersion {
-	fn default() -> Self {
-		StateVersion::V1
-	}
-}
-
 impl From<StateVersion> for u8 {
 	fn from(version: StateVersion) -> u8 {
 		version as u8