Introduce `frame_system::Pallet::run_to_block`,
`frame_system::Pallet::run_to_block_with`, and
`frame_system::RunToBlockHooks` to establish a generic `run_to_block`
mechanism for mock tests, minimizing redundant implementations across
various pallets.

Closes #299.

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Polkadot address: 156HGo9setPcU2qhFMVWLkcmtCEGySLwNqa3DaEiYSWtte4Y

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Signed-off-by: Xavier Lau <x@acg.box>
Co-authored-by: Bastian Köcher <git@kchr.de>
Co-authored-by: command-bot <>
Co-authored-by: Guillaume Thiolliere <guillaume.thiolliere@parity.io>
Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>