Move overlap_mode into trait level attribute + feature flag

compiler/rustc_span/src/symbol.rs

@@ -1205,7 +1205,6 @@ symbols! {
         rustc_trivial_field_reads,
         rustc_unsafe_specialization_marker,
         rustc_variance,
-        rustc_with_negative_coherence,
         rustdoc,
         rustdoc_internals,
         rustfmt,
@@ -1489,6 +1488,7 @@ symbols! {
         width,
         windows,
         windows_subsystem,
+        with_negative_coherence,
         wrapping_add,
         wrapping_mul,
         wrapping_sub,