Rollup merge of #118456 - aDotInTheVoid:unused-symbols, r=WaffleLapkin

rustc_span: Remove unused symbols.

As noted  here, there is no guarantee that all pre-interned symbols are used.

https://github.com/rust-lang/rust/blob/b10cfcd65fd7f7b1ab9beb34798b2108de003452/compiler/rustc_span/src/symbol.rs#L124-L125

This was done starting with using ripgrep to search for `sym::whatever`. I removed anything that didn't show up. However this had a huge number of false positives, due to extensive macro use. Then there was a manual phase of adding back all the ones used my macros.

I don't think this was worth my time to do, but it's done now . ¯\_(ツ)_/¯

compiler/rustc_span/src/symbol.rs

@@ -128,13 +128,11 @@ symbols! {
         AcqRel,
         Acquire,
         AddToDiagnostic,
-        Alignment,
         Any,
         Arc,
         ArcWeak,
         Argument,
         ArgumentMethods,
-        Arguments,
         ArrayIntoIter,
         AsMut,
         AsRef,
@@ -164,7 +162,6 @@ symbols! {
         Break,
         C,
         CStr,
-        CString,
         Capture,
         Center,
         Cleanup,
@@ -174,7 +171,6 @@ symbols! {
         Context,
         Continue,
         Copy,
-        Count,
         Cow,
         Debug,
         DebugStruct,
@@ -199,7 +195,6 @@ symbols! {
         Fn,
         FnMut,
         FnOnce,
-        FormatSpec,
         Formatter,
         From,
         FromIterator,
@@ -208,8 +203,6 @@ symbols! {
         FsPermissions,
         Future,
         FutureOutput,
-        FxHashMap,
-        FxHashSet,
         GlobalAlloc,
         Hash,
         HashMap,
@@ -253,7 +246,6 @@ symbols! {
         NonZeroI32,
         NonZeroI64,
         NonZeroI8,
-        NonZeroIsize,
         NonZeroU128,
         NonZeroU16,
         NonZeroU32,
@@ -275,7 +267,6 @@ symbols! {
         Path,
         PathBuf,
         Pending,
-        Pin,
         Pointer,
         Poll,
         ProcMacro,
@@ -333,7 +324,6 @@ symbols! {
         TyCtxt,
         TyKind,
         Unknown,
-        UnsafeArg,
         Vec,
         VecDeque,
         Wrapper,
@@ -389,7 +379,6 @@ symbols! {
         allow_fail,
         allow_internal_unsafe,
         allow_internal_unstable,
-        allowed,
         alu32,
         always,
         and,
@@ -405,8 +394,6 @@ symbols! {
         arm,
         arm_target_feature,
         array,
-        arrays,
-        as_mut_ptr,
         as_ptr,
         as_ref,
         as_str,
@@ -589,7 +576,6 @@ symbols! {
         const_try,
         constant,
         constructor,
-        context,
         convert_identity,
         copy,
         copy_closures,
@@ -776,8 +762,6 @@ symbols! {
         field,
         field_init_shorthand,
         file,
-        fill,
-        flags,
         float,
         float_to_int_unchecked,
         floorf32,
@@ -1059,7 +1043,6 @@ symbols! {
         mir_unwind_unreachable,
         mir_variant,
         miri,
-        misc,
         mmx_reg,
         modifiers,
         module,
@@ -1157,9 +1140,7 @@ symbols! {
         omit_gdb_pretty_printer_section,
         on,
         on_unimplemented,
-        oom,
         opaque,
-        ops,
         opt_out_copy,
         optimize,
         optimize_attribute,
@@ -1217,7 +1198,6 @@ symbols! {
         pointer,
         pointer_like,
         poll,
-        position,
         post_dash_lto: "post-lto",
         powerpc_target_feature,
         powf32,
@@ -1226,7 +1206,6 @@ symbols! {
         powif64,
         pre_dash_lto: "pre-lto",
         precise_pointer_size_matching,
-        precision,
         pref_align_of,
         prefetch_read_data,
         prefetch_read_instruction,
@@ -1236,7 +1215,6 @@ symbols! {
         prelude,
         prelude_import,
         preserves_flags,
-        primitive,
         print_macro,
         println_macro,
         proc_dash_macro: "proc-macro",
@@ -1260,7 +1238,6 @@ symbols! {
         ptr_const_is_null,
         ptr_copy,
         ptr_copy_nonoverlapping,
-        ptr_drop_in_place,
         ptr_eq,
         ptr_from_ref,
         ptr_guaranteed_cmp,
@@ -1622,7 +1599,6 @@ symbols! {
         structural_match,
         structural_peq,
         structural_teq,
-        sty,
         sub,
         sub_assign,
         sub_with_overflow,
@@ -1744,7 +1720,6 @@ symbols! {
         unrestricted_attribute_tokens,
         unsafe_block_in_unsafe_fn,
         unsafe_cell,
-        unsafe_cell_from_mut,
         unsafe_cell_raw_get,
         unsafe_no_drop_flag,
         unsafe_pin_internals,
@@ -1769,7 +1744,6 @@ symbols! {
         used_with_arg,
         using,
         usize,
-        v1,
         va_arg,
         va_copy,
         va_end,
@@ -1801,7 +1775,6 @@ symbols! {
         wasm_import_module,
         wasm_target_feature,
         while_let,
-        width,
         windows,
         windows_subsystem,
         with_negative_coherence,