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/zig/parser_test.zig

@@ -2548,7 +2548,7 @@ test "zig fmt: same-line comment after non-block if expression" {
 test "zig fmt: same-line comment on comptime expression" {
     try testCanonical(
         \\test "" {
-        \\    comptime assert(@typeInfo(T) == .Int); // must pass an integer to absInt
+        \\    comptime assert(@typeInfo(T) == .int); // must pass an integer to absInt
         \\}
         \\
     );