Add semantic test for SELFBALANCE in inline assembly

test/libsolidity/semanticTests/inlineAssembly/selfbalance.sol

@@ -0,0 +1,12 @@
+contract C {
+    function f() public payable returns (uint ret) {
+        assembly {
+            ret := selfbalance()
+        }
+    }
+}
+// ====
+// EVMVersion: >=istanbul
+// compileViaYul: also
+// ----
+// f(), 254 ether -> 254