[Enhancement]: Unit test for ensuring finalization works after reorg

[kamilsa]

Description

Polkadot-SDK version 1.15 contains a fix of potential finality stall after reorg:
paritytech/polkadot-sdk#5153

It was the case that in Polkadot SDK best_chain_containing on previously prevoted block could return None if reorg happened. Task is to write the same unit test in KAGOME and ensure that this bug is not the case in our implementation

https://github.com/paritytech/polkadot-sdk/pull/5153/files#diff-2abb97f1751549dcc1eb9422bcfc27837e30af682fe3aa32f9bed833883be334R1827

Motivation

Ensures that finality cannot stall after reorg

Additional context

No response

Are you planning to do it yourself in a pull request ?

No