feat: add bitwise NOT operator (~) with token, parser, and native implementation

Add TOKEN_TILDE token type and lexer support for the '~' character in the compiler. Implement the bitwise NOT operation as a native method on the Num class, operating on 32-bit unsigned integers. Include a new OPERATOR macro for prefix/infix operator grammar rules and add comprehensive test cases covering positive, negative, floating-point, and boundary values.

test/assignment/associativity.wren

@@ -0,0 +1,9 @@
+var a = "a"
+var b = "b"
+var c = "c"
+
+// Assignment is right-associative.
+a = b = c
+io.write(a) // expect: c
+io.write(b) // expect: c
+io.write(c) // expect: c