[TODO] Remove ChainState: (3) Improve tracking of Consensus tip with ChainIndexer tip

[quantumagi]

https://app.clickup.com/t/1zvm0j2

The purpose of ChainIndexer is to index the consensus blocks. As such we want to reliably synchronise the updating of the chain indexer tip with the updating of the consensus tip. This is already being accomplished to some extent via twin calls such as these:

                lock (this.peerLock)
                {
                    this.SetConsensusTipInternalLocked(current.Previous);
                    this.chainIndexer.Remove(current);
                }

and

                    lock (this.peerLock)
                    {
                        this.SetConsensusTipInternalLocked(lastValidatedBlockHeader);
                        this.chainIndexer.Add(lastValidatedBlockHeader);
                    }

However there are instances where this is not being done as rigorously:

            // After successfully connecting all blocks set the tree tip and claim the branch.
            List<int> peersToResync = this.SetConsensusTip(lastValidatedBlockHeader, blockMined);

This PR fixes that by updating the chain indexer tip within SetConsensusTip.

In fact it may be a good idea to only update the chain indexer tip from within SetConsensusTip. Tests may be an exception.

Having a ChainIndexer tip that reliably tracks the ConsensusTip would make it easier to get rid of the corresponding field held within ChainState. Some preliminary tests have shown that the substitution works and these changes make the approach safer.