[test] Regression Test Improvements

In the last week we've seen some flakiness in the regression tests due to timeouts on the block creation requests. This will make the tests exit once one is failed in the case of a race, so retrying need not wait on all the tests to finish. Also will fiddle with a few parameters while this is in draft to see if we can speed up the full job and/or reduce flakiness.

Addendum - after some test runs, this makes changes to slow test blocks down by 50%, but increase the parallelism. Additionally it starts the longest running tests first to avoid waiting on the long tail at the end of the run. The end result appears both faster total execution and less flaky.