Release concurrency locks when supervisor fails the jobs handled by workers

[nerisa]

When workers 'die' because of various reasons, the supervisor unlocks the jobs that were being handled by those workers by deleting the claimed_executions for the job and creating failed_executions. However, it does not release any concurrency locks taken by the jobs. This can be an issue if the concurrency limit was reached for the job because no further jobs can run until the concurrency duration is reached.

In this PR, I call job.unblock_next_blocked_job when the supervisor releases all claimed executions of the worker.

Fixes #546

[nerisa]

I couldnt figure out why test/integration/processes_lifecycle_test.rb:171 fails. If I run the test file independently, it passes but when I run the whole test suite, I get the same error as in the CI.

[rosa]

Hey @nerisa, thanks a lot for submitting this PR and sorry for the delay! This looks great. I think the failure is due to that test being flaky in some circumstances. I've got it pending to make them completely stable 😳