Move `type Migrations` to `Config` (#14309)

* move migrate sequence to config

* remove commented out code

* Update frame/contracts/src/lib.rs

Co-authored-by: PG Herveou <pgherveou@gmail.com>

* remove Migrations generic

* make runtime use noop migrations

* restrict is_upgrade_supported

* undo is_upgrade_supported change

* Update bin/node/runtime/src/lib.rs

Co-authored-by: PG Herveou <pgherveou@gmail.com>

* add rust doc example for `Migrations`

* feature gate NoopMigration

* fix example code

* improve example

---------

Co-authored-by: PG Herveou <pgherveou@gmail.com>