Bad blocks RPC + reporting (#9433)

* Bad blocks RPC.

* Return bad blocks via RPC.

* Fix test.

* More verbose bad block message.

* Expose via CLI.

* Remove stray whitespace.

* Remove stray newline.

* Fix tests.

util/memory_cache/src/lib.rs

@@ -86,6 +86,11 @@ impl<K: Eq + Hash, V: HeapSizeOf> MemoryLruCache<K, V> {
 	pub fn current_size(&self) -> usize {
 		self.cur_size
 	}
+
+	/// Get backing LRU cache instance (read only)
+	pub fn backstore(&self) -> &LruCache<K, V> {
+		&self.inner
+	}
 }
 
 #[cfg(test)]