Move parse-fail tests to UI

src/test/ui/parser/raw-byte-string-eof.stderr

@@ -0,0 +1,10 @@
+error: unterminated raw string
+  --> $DIR/raw-byte-string-eof.rs:15:6
+   |
+LL |     br##"a"#;  //~ unterminated raw string
+   |      ^ unterminated raw string
+   |
+   = note: this raw string should be terminated with `"##`
+
+error: aborting due to previous error
+