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/comparison.wren

@@ -1,27 +1,27 @@
-io.write(1 < 2)    // expect: true
-io.write(2 < 2)    // expect: false
-io.write(2 < 1)    // expect: false
+IO.write(1 < 2)    // expect: true
+IO.write(2 < 2)    // expect: false
+IO.write(2 < 1)    // expect: false
 
-io.write(1 <= 2)    // expect: true
-io.write(2 <= 2)    // expect: true
-io.write(2 <= 1)    // expect: false
+IO.write(1 <= 2)    // expect: true
+IO.write(2 <= 2)    // expect: true
+IO.write(2 <= 1)    // expect: false
 
-io.write(1 > 2)    // expect: false
-io.write(2 > 2)    // expect: false
-io.write(2 > 1)    // expect: true
+IO.write(1 > 2)    // expect: false
+IO.write(2 > 2)    // expect: false
+IO.write(2 > 1)    // expect: true
 
-io.write(1 >= 2)    // expect: false
-io.write(2 >= 2)    // expect: true
-io.write(2 >= 1)    // expect: true
+IO.write(1 >= 2)    // expect: false
+IO.write(2 >= 2)    // expect: true
+IO.write(2 >= 1)    // expect: true
 
 // Zero and negative zero compare the same.
-io.write(0 < -0) // expect: false
-io.write(-0 < 0) // expect: false
-io.write(0 > -0) // expect: false
-io.write(-0 > 0) // expect: false
-io.write(0 <= -0) // expect: true
-io.write(-0 <= 0) // expect: true
-io.write(0 >= -0) // expect: true
-io.write(-0 >= 0) // expect: true
+IO.write(0 < -0) // expect: false
+IO.write(-0 < 0) // expect: false
+IO.write(0 > -0) // expect: false
+IO.write(-0 > 0) // expect: false
+IO.write(0 <= -0) // expect: true
+IO.write(-0 <= 0) // expect: true
+IO.write(0 >= -0) // expect: true
+IO.write(-0 >= 0) // expect: true
 
 // TODO: Wrong type for RHS.