Implement parsing annotations and modifiers starting with '@'

compiler/testData/psi/annotation/at/validExpressions.kt

@@ -0,0 +1,31 @@
+fun foo() {
+    return @ann 1
+    return (@ann 2)
+
+    @ann foo("")
+
+    @ann 3 + @ann 4 * @ann("") 5 infix @ann 6
+
+    foo.bar(@ann fun(x: Int) {
+
+    })
+
+    @ann if (@ann true || true) {
+
+    }
+    else {}
+
+    for (i in @ann x) {}
+
+    label@ @ann while (true) {
+        @ann break@label
+    }
+
+    return@label @ann 1
+
+    label@simpleName
+
+    val x = @ann [ann] l@{
+        a, b, c -> a
+    }
+}