Implement PrecommitActions interface for Client type

[timwu20]

Issue Summary

Taken from design doc regarding PreCommitActions (link):

PreCommitActions is a trait that allows you to perform registered actions on block import and/or updated finality. The actions are performed before committing to the underlying db.

/// Callback invoked before committing the operations created during block import.
/// This gives the opportunity to perform auxiliary pre-commit actions and optionally
/// enqueue further storage write operations to be atomically performed on commit.
pub type OnImportAction<Block> =
	Box<dyn (Fn(&BlockImportNotification<Block>) -> AuxDataOperations) + Send>;

/// Callback invoked before committing the operations created during block finalization.
/// This gives the opportunity to perform auxiliary pre-commit actions and optionally
/// enqueue further storage write operations to be atomically performed on commit.
pub type OnFinalityAction<Block> =
	Box<dyn (Fn(&FinalityNotification<Block>) -> AuxDataOperations) + Send>;

/// Interface to perform auxiliary actions before committing a block import or
/// finality operation.
pub trait PreCommitActions<Block: BlockT> {
	/// Actions to be performed on block import.
	fn register_import_action(&self, op: OnImportAction<Block>);

	/// Actions to be performed on block finalization.
	fn register_finality_action(&self, op: OnFinalityAction<Block>);
}

For OnImportAction you receive a BlockImportNotification and you're expected to return AuxDataOperations which is already introduced in PR #4405. The AuxStore interface is already introduced and implemented by db.Backend.

The PreCommitActions trait/interface is not used by any BlockState or StorageState functionality. Rather it will be used for future work regarding BEEFY and GRANDPA.

Acceptance Criteria

• Introduction of PreCommitActions interface
• Implementation of PreCommitActions interface.
• Tests

Other Information and useful links

• substrate reference to PreCommitActions.