vec (+swizzle) and annotated_arg should define their binary operators as hidden friends

[rolandschulz]

Both vec (+swizzle) and annotated_arg don't define the their binary operators as hidden friends. For vec the spec is clear that it should be a hidden friend. For annotated_arg we should make this clear.

Originally posted by @rolandschulz in #11971 (comment)

[steffenlarsen]

For vec and swizzle this is addressed in #12396.

[steffenlarsen]

These have been addressed:

• vec: [SYCL] Change vec operators to be friends #12396
• Swizzles: [SYCL] Make swizzle mutating operators const friends #13012
• annotated_arg: [SYCL] refactor annotated_arg operator forwarding #12232

@rolandschulz - I will close this. Please reopen if you believe we missed something.