[Sol->Yul] Implementing push for nested storage arrays and storage arrays of structs.

test/libsolidity/semanticTests/structs/struct_storage_push_zero_value.sol

@@ -0,0 +1,28 @@
+contract C {
+    struct S {
+        uint256 x;
+        uint128 y;
+        uint32 z;
+        uint128[3] a1;
+        uint128[] a2;
+    }
+    uint8 b = 23;
+    S[] s;
+    uint8 a = 17;
+    function f() public {
+        s.push();
+        assert(s[0].x == 0);
+        assert(s[0].y == 0);
+        assert(s[0].z == 0);
+        assert(s[0].a1[0] == 0);
+        assert(s[0].a1[1] == 0);
+        assert(s[0].a1[2] == 0);
+        assert(s[0].a2.length == 0);
+        assert(b == 23);
+        assert(a == 17);
+    }
+}
+// ====
+// compileViaYul: also
+// ----
+// f() ->