Improve try_get_chain_position the logic

[notmandatory]

"In try_get_chain_position the logic to filter out confirmed ancestors was copy-pasted for the descendants (you can see as the comment wasn't updated, it still mentions "We're filtering the ancestors"). But if a confirmed descendant is encountered it means the transaction is confirmed too, so it could shortcut?"

[oleonardolima]

It can be closed now, as #1670 has been merged, right ?

[notmandatory]

Yes you're right, the try_get_chain_position function was removed in #1670 so we can close this one now too.