behavior: fix issues with x86_64 backend tests

 * Oops, I accidentally disabled most of them.
 * Cleanup some workarounds for now closed issues.
 * Test binary operations with more scalar integer types.

Author: jacobly0

test/behavior/x86_64.zig

@@ -7,6 +7,8 @@ test {
     if (builtin.object_format == .macho) return error.SkipZigTest;
     // COFF linker does not support the new backend.
     if (builtin.object_format == .coff) return error.SkipZigTest;
-    _ = @import("x86_64/math.zig");
+    _ = @import("x86_64/binary.zig");
+    _ = @import("x86_64/cast.zig");
     _ = @import("x86_64/mem.zig");
+    _ = @import("x86_64/unary.zig");
 }