Transaction factory (#2481)

* Fix typos

* Add transaction factory

`cargo run -- purge-chain -y --chain dev && cargo run -- --dev --transaction-factory 10`

* Fix comment and remove build deps

* Move crate to test-utils

* Switch from flag to subcommand

`cargo run -- factory --dev --num 5`

* Decouple factory from node specifics

* Introduce different manufacturing modes

* Remove unrelated changes

* Update Cargo.lock

* Use SelectChain to fetch best block

* Improve expect proof

* Panic if factory executed with unsupported chain spec

* Link ToDo comments to follow-up ticket

* Address comments and improve style

* Remove unused dependencies

* Fix indent level

* Replace naked unwrap

* Update node/cli/src/factory_impl.rs

* Fix typo

* Use inherent_extrinsics instead of timestamp

* Generalize factory and remove saturated conversions

* Format imports

* Make it clearer that database needs to be empty

* Ensure factory settings

* Apply suggestions from code review

Co-Authored-By: Bastian Köcher <[email protected]>

* Update test-utils/transaction-factory/src/lib.rs

Co-Authored-By: Bastian Köcher <[email protected]>

* Fix match guard syntax

* Simplify import, remove empty line

* Update node/cli/Cargo.toml

* Update lockfile