v5.2.6: Fix step hanging after a failed cache restore

The action now exits as soon as its work is done. Before this release, a cache restore that failed during the download could leave the step running for up to ten minutes after setup had finished.

Fixed

• A failed cache restore no longer leaves the step hanging. If the mise cache download failed partway through, for example with getaddrinfo EAI_AGAIN, the action logged a warning, installed the tools and saved the cache, then stopped producing output. The step stayed in progress until the job was cancelled or a timer inside @actions/cache fired after 10 minutes. That timer is left running when a download fails (actions/toolkit#2470), and it kept the Node process alive. The action now exits explicitly after both the main step and the post step finish. It waits up to 5 seconds for log output to flush, then exits. The exit code set by any earlier failure is kept. Errors that aren't Error objects now mark the step as failed with their message. Before, they caused an unhandled rejection. (#718 by @jdx and @kjanat, fixes #717)

Full Changelog: v5.2.5...v5.2.6