P3560 R1 Error Handling in Reflection

[wg21bot]

P3560R0 Error Handling in Reflection (Barry Revzin, Peter Dimov)

[hanickadot]

This paper is modification of P2996 to throw exceptions, as already preferred variants. SG7 doesn't need to see this paper. LEWG should do the design review of exception types.

[tahonermann]

@inbal2l, I think this paper is targeting C++26. Can you confirm?