add zero and clear

sub/core/src/arrays.rs

@@ -57,6 +57,11 @@ impl<const MAX_LEN: usize, T: Sized> FixedVec<MAX_LEN, T> {
         unsafe { core::slice::from_raw_parts_mut(self.buffer.as_mut_ptr() as *mut T, self.length) }
     }
 
+    pub fn zero_and_clear(&mut self) {
+        self.as_slice_mut().fill(0);
+        self.length = 0;
+    }
+
     pub fn clear(&mut self) {
         self.length = 0;
     }