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/list/eof_after_comma.wren

@@ -0,0 +1,2 @@
+[1, 2,
+// expect error

test/language/list/eof_after_element.wren

@@ -0,0 +1,2 @@
+[1, 2
+// expect error

test/language/list/grow_shrink.wren

@@ -0,0 +1,11 @@
+// This mostly tests that lists handle growing and shrinking their memory.
+var list = []
+for (i in 0..200) {
+  list.add(i)
+}
+
+for (i in 0..195) {
+  list.removeAt(-1)
+}
+
+IO.print(list) // expect: [0, 1, 2, 3, 4]

test/language/list/newline_before_comma.wren

@@ -0,0 +1,2 @@
+var list = ["a"
+, "b"] // expect error

test/language/list/newlines.wren

@@ -0,0 +1,10 @@
+// Allow after '[' and ',', and before ']'.
+var list = [
+
+"a",
+"b"
+
+]
+
+IO.print(list[0]) // expect: a
+IO.print(list[1]) // expect: b