fix: disregard tx count if the stacks tip has changed

[obycode]

When mining, if the Stacks tip changes, then we no longer want to compare the transaction count of a newly mined block with that of the previously mined block, since the previous block is now a reorg.

Fixes #5157.

[obycode]

This still needs an integration test.

[hstove]

Plan for integration test:

• Two miners
• Miner A finishes a tenure and miner B submits a block commit before seeing the last block of A's tenure
• B's commit is committing to a block (of A's) that has something like 4 tx's
• Then, B gets the new block from A and builds off of it
• When B tries to make a block, it only has two tx's available, because 2 of them were in A's last block
• Without this PR's change, the miner would get stuck. The test should verify that B can make the new block just fine

[obycode]

Plan for integration test:

• Two miners
• Miner A finishes a tenure and miner B submits a block commit before seeing the last block of A's tenure
• B's commit is committing to a block (of A's) that has something like 4 tx's
• Then, B gets the new block from A and builds off of it
• When B tries to make a block, it only has two tx's available, because 2 of them were in A's last block
• Without this PR's change, the miner would get stuck. The test should verify that B can make the new block just fine

This sounds good, except in the last bullet, it's not that the miner would get stuck, but it would mine a sibling block, instead of building off of the latest tip, so we would not see the chain length increase and we would see two blocks at the same height.

[blockstack-devops]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.