don't point at const usage site for resolution-time errors

also share the code that emits the actual error

Author: RalfJung

tests/fail/const-ub-checks.stderr

@@ -4,7 +4,7 @@ error[E0080]: evaluation of constant value failed
 LL |     ptr.read();
    |     ^^^^^^^^^^ accessing memory with alignment ALIGN, but alignment ALIGN is required
 
-note: erroneous constant used
+note: erroneous constant encountered
   --> $DIR/const-ub-checks.rs:LL:CC
    |
 LL |     let _x = UNALIGNED_READ;

tests/fail/erroneous_const.stderr

@@ -6,7 +6,7 @@ LL |     const VOID: ! = panic!();
    |
    = note: this error originates in the macro `$crate::panic::panic_2021` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-note: erroneous constant used
+note: erroneous constant encountered
   --> $DIR/erroneous_const.rs:LL:CC
    |
 LL |         let _ = PrintName::<T>::VOID;

tests/fail/erroneous_const2.stderr

@@ -4,13 +4,13 @@ error[E0080]: evaluation of constant value failed
 LL | const FOO: u32 = [X - Y, Y - X][(X < Y) as usize];
    |                   ^^^^^ attempt to compute `5_u32 - 6_u32`, which would overflow
 
-note: erroneous constant used
+note: erroneous constant encountered
   --> $DIR/erroneous_const2.rs:LL:CC
    |
 LL |     println!("{}", FOO);
    |                    ^^^
 
-note: erroneous constant used
+note: erroneous constant encountered
   --> $DIR/erroneous_const2.rs:LL:CC
    |
 LL |     println!("{}", FOO);