Changelog and test for the KeccakCaching bug

test/libsolidity/semanticTests/inlineAssembly/keccak256_optimizer_cache_bug.sol

@@ -0,0 +1,21 @@
+contract C {
+  uint[] data;
+
+  function val() public returns (bool) {
+    assembly {
+        sstore(0, 2)
+        mstore(0, 0)
+        sstore(keccak256(0, 32), 234)
+        // A bug in the caching mechanism previously caused keccak256(0, 23) to be the same as
+        // keccak256(0, 32), leading to `data[1] == 123` being true.
+        sstore(add(keccak256(0, 23), 1), 123)
+    }
+    assert(data[1] != 123);
+    assert(data[1] == 0);
+    return true;
+  }
+}
+// ====
+// compileViaYul: also
+// ----
+// val() -> true