message: Cleanup metadata codegen slightly
diff: @@ -68,7 +68,9 @@ impl Metadata<'_> {
  let contract_ident = self.contract.module().storage().ident();
  quote! {
  <#contract_ident as ::ink_storage::traits::StorageLayout>::layout(
  - &mut ::ink_primitives::KeyPtr::from(::ink_primitives::Key::from([0x00; 32]))
  + &mut <::ink_primitives::KeyPtr as ::core::convert::From<::ink_primitives::Key>>::from(
  + <::ink_primitives::Key as ::core::convert::From<[::core::primitive::u8; 32]>>::from([0x00_u8; 32])
  + )
  )
  }
  }
  @@ -81,16 +83,16 @@ impl Metadata<'_> {
  quote! {
  ::ink_metadata::ContractSpec::new()
  - .constructors(vec![
  + .constructors([
  #(#constructors ,)*
  ])
  - .messages(vec![
  + .messages([
  #(#messages ,)*
  ])
  - .events(vec![
  + .events([
  #(#events ,)*
  ])
  - .docs(vec![
  + .docs([
  #(#docs ,)*
  ])
  .done()
  @@ -156,10 +158,10 @@ impl Metadata<'_> {
  quote_spanned!(span =>
  ::ink_metadata::ConstructorSpec::#constr
  .selector([#(#selector_bytes),*])
  - .args(vec![
  + .args([
  #(#args ,)*
  ])
  - .docs(vec![
  + .docs([
  #(#docs ,)*
  ])
  .done()
  @@ -202,7 +204,8 @@ impl Metadata<'_> {
  .collect::<Vec<_>>();
  quote! {
  ::ink_metadata::TypeSpec::with_name_segs::<#ty, _>(
  - vec![#(#segs),*].into_iter().map(AsRef::as_ref)
  + ::core::iter::IntoIterator::into_iter([#(#segs),*])
  + .map(::core::convert::AsRef::as_ref)
  )
  }
  } else {
  @@ -250,13 +253,13 @@ impl Metadata<'_> {
  quote_spanned!(span =>
  ::ink_metadata::MessageSpec::#constr
  .selector([#(#selector_bytes),*])
  - .args(vec![
  + .args([
  #(#args ,)*
  ])
  .returns(#ret_ty)
  .mutates(#mutates)
  .payable(#is_payable)
  - .docs(vec![
  + .docs([
  #(#docs ,)*
  ])
  .done()
  @@ -291,10 +294,10 @@ impl Metadata<'_> {
  let args = Self::generate_event_args(event);
  quote_spanned!(span =>
  ::ink_metadata::EventSpec::new(#ident_lit)
  - .args(vec![
  + .args([
  #( #args, )*
  ])
  - .docs(vec![
  + .docs([
  #( #docs, )*
  ])
  .done()
  @@ -316,7 +319,7 @@ impl Metadata<'_> {
  ::ink_metadata::EventParamSpec::new(#ident_lit)
  .of_type(#ty)
  .indexed(#is_topic)
  - .docs(vec![
  + .docs([
  #( #docs, )*
  ])
  .done()
  