Integration Test - Activation Block is Flashblock

[ASuciuX]

Test that if the 3 blocks in the activation are flashblocks and everything still happens as expected. If block 131 is activation block -> blocks 130, 131, 132 as flashblocks being created very fast without enough time for setting the migration.

Check this test This is the function to modify for testing the scenario. Stop 1 block right before epoch3 starts and mine 3 blocks quickly

run_until_burnchain_height(
        btc_regtest_controller,
        &blocks_processed,
        epoch_3.start_height - 1, // change to -2
        &naka_conf,
    );