refactor: convert IO from singleton instance to static class with metaclass native methods

Replace the global `io` singleton object with a static `IO` class, moving the `write` native from the instance to the metaclass. Update all benchmark, example, and test files to use `IO.write()` instead of `io.write()`.

test/number/bitwise_not.wren

@@ -1,22 +1,22 @@
-io.write(~0) // expect: 4294967295
-io.write(~1) // expect: 4294967294
-io.write(~23) // expect: 4294967272
+IO.write(~0) // expect: 4294967295
+IO.write(~1) // expect: 4294967294
+IO.write(~23) // expect: 4294967272
 
 // Max u32 value.
-io.write(~4294967295) // expect: 0
+IO.write(~4294967295) // expect: 0
 
 // Past max u32 value.
-io.write(~4294967296) // expect: 4294967295
+IO.write(~4294967296) // expect: 4294967295
 
 // Negative numbers.
-io.write(~-1) // expect: 0
-io.write(~-123) // expect: 122
-io.write(~-4294967294) // expect: 4294967293
-io.write(~-4294967295) // expect: 4294967294
-io.write(~-4294967296) // expect: 4294967295
+IO.write(~-1) // expect: 0
+IO.write(~-123) // expect: 122
+IO.write(~-4294967294) // expect: 4294967293
+IO.write(~-4294967295) // expect: 4294967294
+IO.write(~-4294967296) // expect: 4294967295
 
 // Floating point values.
-io.write(~1.23) // expect: 4294967294
-io.write(~0.00123) // expect: 4294967295
-io.write(~345.67) // expect: 4294966950
-io.write(~-12.34) // expect: 11
+IO.write(~1.23) // expect: 4294967294
+IO.write(~0.00123) // expect: 4294967295
+IO.write(~345.67) // expect: 4294966950
+IO.write(~-12.34) // expect: 11