(PE-3657) Addressed some PR feedback

This commit includes the following changes:

* Removed validation of the shutdown reason promise since it relied upon
  Clojure implementation details that may not hold true in the future.

* Pushed try/catch for logging lifecycle function errors down into
  `run-lifecycle-fn` to avoid repeating the same code in the calling
  layer.

* Moved `translate-app-shutdown-error-into-throwable` from testutils
  to app->shutdown-error-throwable-or-app in the production internal
  namespace.  Follows function naming convention for conversion and
  available for later application reuse.
(PE-3657) Added check-for-errors! to App and reworked reloaded example

This commit adds a `check-for-errors!` function to the TrapperkeeperApp.
The function is used by the reloaded repl example in the README.md to
propagate any errors captured during the init and/or start phase of the
bootstrap process up as a java.lang.Throwable.