Reorganize tests and benchmark scripts.

Mainly to get rid of one top level directory. But this will
also be useful when there are tests of the embedding API.

test/language/bitwise_precedence.wren

@@ -0,0 +1,23 @@
+// << have higher precedence than |.
+IO.print(2 | 1 << 1) // expect: 2
+IO.print(1 << 1 | 2) // expect: 2
+
+// << has higher precedence than &.
+IO.print(2 & 1 << 1) // expect: 2
+IO.print(1 << 1 & 2) // expect: 2
+
+// << has higher precedence than ^.
+IO.print(2 ^ 1 << 1) // expect: 0
+IO.print(1 << 1 ^ 2) // expect: 0
+
+// & has higher precedence than |.
+IO.print(1 & 1 | 2) // expect: 3
+IO.print(2 | 1 & 1) // expect: 3
+
+// & has higher precedence than ^.
+IO.print(1 & 1 ^ 2) // expect: 3
+IO.print(2 ^ 1 & 1) // expect: 3
+
+// ^ has higher precedence than |.
+IO.print(1 ^ 1 | 1) // expect: 1
+IO.print(1 | 1 ^ 1) // expect: 1