Migration testing runtime API/Bot (#8038)

* A clean new attempt

* Checkpoint to move remote.

* A lot of dependency wiring to make it feature gated.

* bad macro, bad macro.

* Undo the DB mess.

* Update frame/support/src/traits.rs

Co-authored-by: Alexander Popiak <alexander.popiak@parity.io>

* Apply suggestions from code review

Co-authored-by: Alexander Popiak <alexander.popiak@parity.io>

* unbreak the build

* Update frame/try-runtime/src/lib.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Update utils/frame/try-runtime/cli/Cargo.toml

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>

* Update frame/try-runtime/Cargo.toml

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>

* Address most review grumbles.

* Fix build

* Add some comments

* Remove allowing one pallet at a time.

* More grumbles.

* relocate remote-ext

* Fix build

Co-authored-by: Alexander Popiak <alexander.popiak@parity.io>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>