[FRAME Core] Adds ability to split a pallet across multiple files (#13950)

* Initial setup

* Updates macro_magic version and refactors accordingly

* Removes unwrap from macro

* Splits into multiple sections

* Uses call_site to fix macro hygiene issue

* Initial setup

* Removes unnecessary changes

* Moves template palet back

* Updates cargo.lock

* Moves BagsList inside mod

* Comments access to internal functions for now

* Updates tests

* Uncomments code

* Fixes test

* Moves bags-list to separate crate

* Initial setup

* Removes bags-list changes

* Fix structure

* Minor update

* Addresses review comment

* Adds a couple of UI tests. More to be added

* Adds err files

* Adds test for no pallet

* Adds doc

* Updates versions

* Adds benchmarking

* Updates doc link

* ".git/.scripts/commands/fmt/fmt.sh"

* Minor update

* Adds missing changes

* ".git/.scripts/commands/fmt/fmt.sh"

* Update frame/support/procedural/src/lib.rs

Co-authored-by: Sam Johnson <sam@durosoft.com>

* Addresses review comments

* Addresses review comments

* ".git/.scripts/commands/fmt/fmt.sh"

* Update frame/support/procedural/src/lib.rs

Co-authored-by: Sam Johnson <sam@durosoft.com>

* Update frame/support/procedural/src/lib.rs

Co-authored-by: Sam Johnson <sam@durosoft.com>

* Update frame/support/procedural/src/lib.rs

Co-authored-by: Sam Johnson <sam@durosoft.com>

* Adds UI test for disambiguation

* ".git/.scripts/commands/fmt/fmt.sh"

* Makes clippy happy

* ".git/.scripts/commands/fmt/fmt.sh"

* Fixes frame support test

* Fixes frame support test

* Split items other than storage

* Updates versions

* Fixes some review comments

* Addresses review comments

* ".git/.scripts/commands/fmt/fmt.sh"

* Updates docs

* Adds experimental disclaimer

* ".git/.scripts/commands/fmt/fmt.sh"

* Update frame/support/test/tests/split_ui/no_section_found.rs

Co-authored-by: Sam Johnson <sam@durosoft.com>

* Addresses review comments

* Fixes test

---------

Co-authored-by: command-bot <>
Co-authored-by: command-bot <ci@gitlab.parity.io>
Co-authored-by: Sam Johnson <sam@durosoft.com>

substrate/frame/examples/src/lib.rs

@@ -35,3 +35,6 @@
 //!
 //! - [**`pallet-example-kitchensink`**](./kitchensink): A simple example of a FRAME pallet
 //!   demonstrating a catalog of the the FRAME macros and their various syntax options.
+//!
+//! - [**`pallet-example-split`**](./split): A simple example of a FRAME pallet demonstrating the
+//!   ability to split sections across multiple files.