feat: add == and != operators for bool, number, and string types with type-checking

Implement equality and inequality operators across three primitive types in the compiler and runtime. Add `bool_eqeq`/`bool_bangeq`, `num_eqeq`/`num_bangeq`, and `string_eqeq`/`string_bangeq` primitives that return false/true respectively when comparing against incompatible types. Update the parse rule table with `INFIX_OPERATOR` macros for `TOKEN_EQEQ` and `TOKEN_BANGEQ` at `PREC_COMPARISON` precedence. Include test files `bool_equality.wren`, `number_equality.wren`, and `string_equality.wren` covering cross-type comparisons and edge cases.

test/number_equality.wren

@@ -0,0 +1,19 @@
+io.write(123 == 123)  // expect: true
+io.write(123 == 124)  // expect: false
+io.write(-3 == 3)     // expect: false
+
+// Not equal to other types.
+io.write(123 == "123") // expect: false
+io.write(1 == true)    // expect: false
+io.write(0 == false)   // expect: false
+
+io.write(123 != 123)  // expect: false
+io.write(123 != 124)  // expect: true
+io.write(-3 != 3)     // expect: true
+
+// Not equal to other types.
+io.write(123 != "123") // expect: true
+io.write(1 != true)    // expect: true
+io.write(0 != false)   // expect: true
+
+// TODO(bob): Should 0 == -0?