This refactor bridges some gaps between a long-running feature branch (#49268) and the master branch.
First of all, this PR gives our PackagingTestCase class some methods to start and stop Elasticsearch that will switch on packaging type and delegate to the appropriate utility class for deb/RPM packages, archive installations, and Docker. These methods should be very useful as we continue group tests by function rather than by package or platform type.
Second, the password-protected keystore tests have a particular need to read the output of Elasticsearch startup commands. In order to make this easer to do, some commands now return Shell.Result objects so that tests can check over output to the shell. To that end, there's also an assertElasticsearchFailure method that will handle checking for startup failures for the various distribution types.
There is an update to the Powershell startup script for archives that asynchronously redirects the output of the Powershell process to files that we can read for errors.
Finally, we use the ES_STARTUP_SLEEP_TIME environment variable to make sure that our startup commands wait long enough before exiting for errors to make it to the standard output and error streams.
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