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/test/tests/pallet.rs

@@ -146,6 +146,12 @@ pub mod pallet {
 		fn some_extra_extra() -> T::AccountId {
 			SomeType1.into()
 		}
+
+		/// Some doc
+		#[pallet::constant_name(SomeExtraRename)]
+		fn some_extra_rename() -> T::AccountId {
+			SomeType1.into()
+		}
 	}
 
 	#[pallet::pallet]
@@ -1220,6 +1226,12 @@ fn metadata() {
 					value: vec![0, 0, 0, 0, 0, 0, 0, 0],
 					docs: vec![" Some doc"],
 				},
+				PalletConstantMetadata {
+					name: "SomeExtraRename",
+					ty: meta_type::<u64>(),
+					value: vec![0, 0, 0, 0, 0, 0, 0, 0],
+					docs: vec![" Some doc"],
+				},
 			],
 			error: Some(PalletErrorMetadata { ty: meta_type::<pallet::Error<Runtime>>() }),
 		},