Unusual tokens of builtin AttributeKind

[zjp-CN]

rustc_hir_pretty::attribute_to_string on builtin AttributeKind will emit some unusual attr tokens like the following, but they can be parsed back through syn:

#[test]
fn parse_attr() {
    let attr = r##"
#[attr = ConstStability {stability: PartialConstStability {level:
Stable {since: Version(RustcVersion {major: 1, minor: 65, patch: 0})},
feature: "ptr_const_cast", promotable: false}}]"##;

    use proc_macro2::TokenStream;
    use quote::ToTokens;
    use syn::parse::Parser;
    let attrs = syn::Attribute::parse_outer.parse_str(attr).unwrap();
    let mut ts = TokenStream::new();
    attrs.into_iter().for_each(|attr| ts.extend(attr.into_token_stream()));
    println!("{ts}");
}

To reduce trivial attrs for verification, we just filter out most of these attrs, but for some codegen related one, like Align and Repr.