Implement `fungible::*` for Balances (#8454)

* Reservable, Transferrable Fungible(s), plus adapters.

* Repot into new dir

* Imbalances for Fungibles

* Repot and balanced fungible.

* Clean up names and bridge-over Imbalanced.

* Repot frame_support::trait. Finally.

* Make build.

* Docs

* Good errors

* Fix tests. Implement fungible::Inspect for Balances.

* Implement additional traits for Balances.

* Revert UI test "fixes"

* Fix UI error

* Fix UI test

* More work on fungibles

* Fixes

* More work.

* Update lock

* Make fungible::reserved work for Balances

* Introduce Freezer to Assets, ready for a reserve & locks pallet. Some renaming/refactoring.

* Cleanup errors

* Imbalances working with Assets

* Test for freezer.

* Grumbles

* Grumbles

* Fixes

* Extra "side-car" data for a user's asset balance.

* Fix

* Fix test

* Fixes

* Line lengths

* Comments

* Update frame/assets/src/tests.rs

Co-authored-by: Shawn Tabrizi <[email protected]>

* Update frame/support/src/traits/tokens/fungibles.rs

Co-authored-by: Shawn Tabrizi <[email protected]>

* Update frame/assets/src/lib.rs

Co-authored-by: Shawn Tabrizi <[email protected]>

* Update frame/support/src/traits/tokens/fungible.rs

Co-authored-by: Shawn Tabrizi <[email protected]>

* Introduce `transfer_reserved`

* Rename fungible Reserve -> Hold, add flag structs

* Avoid the `melted` API - its too complex and gives little help

* Repot Assets pallet

Co-authored-by: Bastian Köcher <[email protected]>
Co-authored-by: Shawn Tabrizi <[email protected]>