std: update std.builtin.Type fields to follow naming conventions

The compiler actually doesn't need any functional changes for this: Sema
does reification based on the tag indices of `std.builtin.Type` already!
So, no zig1.wasm update is necessary.

This change is necessary to disallow name clashes between fields and
decls on a type, which is a prerequisite of #9938.

lib/std/debug/Dwarf.zig

@@ -2216,7 +2216,7 @@ pub const ElfModule = struct {
             }
 
             var section_index: ?usize = null;
-            inline for (@typeInfo(Dwarf.Section.Id).Enum.fields, 0..) |sect, i| {
+            inline for (@typeInfo(Dwarf.Section.Id).@"enum".fields, 0..) |sect, i| {
                 if (mem.eql(u8, "." ++ sect.name, name)) section_index = i;
             }
             if (section_index == null) continue;