Now that stalled txs are discarded it causes a couple tests to fail sometimes due to missing txs:

• For the chronik_ws test, we simply bump the stale thresold to a very high value to avoid this situation.
• For the abc_mining_avalanche_preconsensus test, make sure the non-preconsensus node has all the txs in its mempool before finalizing/invlidating any of them. It also requires to finalize/invalidate multiple txs at once instead of one by one to avoid intermediate states where some txs are finalized while their ancestors are not due to missing slots. As a consequence a small change in the def can_find_inv_in_poll is needed that could be leveraged in other tests as well. This also makes the test faster (stalling takes longer than finalizing/invlidating).