Rework no_coverage to coverage(off)

compiler/rustc_span/src/symbol.rs

@@ -573,6 +573,7 @@ symbols! {
         cosf32,
         cosf64,
         count,
+        coverage,
         cr,
         crate_id,
         crate_in_paths,
@@ -1037,7 +1038,6 @@ symbols! {
         no,
         no_builtins,
         no_core,
-        no_coverage,
         no_crate_inject,
         no_debug,
         no_default_passes,
@@ -1068,6 +1068,7 @@ symbols! {
         note,
         object_safe_for_dispatch,
         of,
+        off,
         offset,
         offset_of,
         omit_gdb_pretty_printer_section,