Support extra constant renaming (#9814)

* Rebased with master. Resolved merge conflict in
frame/support/test/tests/pallet.rs

* Switching Account ID to SomeType1, as SomeType3 was giving me conversion error.

* Wrong indent config.  Fixed.

* These tabs look fine locally, but look different on Github.  Trying to get the style config right.

* Parsing pallet::constant_name.
Passing unit tests, which is confusing because I didn't change `ident` in the ExtraConstantDef initialization.

* Finalized parsing of extra constant name by adding optional metadata field.
Added expansion logic that replaces respective `idents` where they exist.

* Erasing this to try to keep the format the same across the source code.

* Another formatting change for consistency.

* Update frame/support/procedural/src/pallet/expand/constants.rs

strictly more idiomatic.

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

* Update frame/support/procedural/src/pallet/parse/extra_constants.rs

strictly idiomatic change.

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

* Fixing formatting and CI warnings.

* switched to nightly compiler to use rustfmt.toml

Co-authored-by: Eric Miller <emiller@lirio.co>
Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

substrate/frame/support/procedural/src/pallet/parse/helper.rs

@@ -139,6 +139,12 @@ impl MutItemAttrs for syn::ItemMod {
 	}
 }
 
+impl MutItemAttrs for syn::ImplItemMethod {
+	fn mut_item_attrs(&mut self) -> Option<&mut Vec<syn::Attribute>> {
+		Some(&mut self.attrs)
+	}
+}
+
 /// Parse for `()`
 struct Unit;
 impl syn::parse::Parse for Unit {