Add annotation-based custom field attributes support

bindgen-tests/tests/headers/field_attributes.h

@@ -0,0 +1,6 @@
+struct S {
+    /// <div rustbindgen attribute="#[deprecated] #[cfg(not(any(foo, bar)))]"></div>
+    int field_1;
+    /// <div rustbindgen attribute="#[cfg(not(baz))]"></div>
+    char field_2;
+};

bindgen/codegen/mod.rs

@@ -1567,19 +1567,29 @@ impl FieldCodegen<'_> for FieldData {
         let accessor_kind =
             self.annotations().accessor_kind().unwrap_or(accessor_kind);
 
+        let attributes: Vec<proc_macro2::TokenStream> = self
+            .annotations()
+            .attributes()
+            .iter()
+            .map(|s| s.parse().unwrap())
+            .collect::<Vec<_>>();
+
         match visibility {
             FieldVisibilityKind::Private => {
                 field.append_all(quote! {
+                    #( #attributes )*
                     #field_ident : #ty ,
                 });
             }
             FieldVisibilityKind::PublicCrate => {
                 field.append_all(quote! {
+                    #( #attributes )*
                     pub(crate) #field_ident : #ty ,
                 });
             }
             FieldVisibilityKind::Public => {
                 field.append_all(quote! {
+                    #( #attributes )*
                     pub #field_ident : #ty ,
                 });
             }

bindgen/ir/annotations.rs

@@ -102,7 +102,7 @@ pub(crate) struct Annotations {
     constify_enum_variant: bool,
     /// List of explicit derives for this type.
     derives: Vec<String>,
-    /// List of explicit attributes for this type.
+    /// List of explicit attributes for this type/field.
     attributes: Vec<String>,
 }