The OpenJDK has a custom timeout handler that can be enabled via the `--enable-jtreg-failure-handler` configure option. Currently, it emits multiple really large HTML files (especially a 50MB+ environment.html), that contain a lot of information on the test system, mostly in the form of a tree-like structure with command output as its leaves.

I propose to add an `--jtreg-failure-handler-output-mode=[html|text]` option (default value is `html`). To change between the current HTML and a text mode, which just doesn't emit a tree-like HTML file, but just files in a directory structure. This would make it easier for CI systems to consume.

Additionally, I'm proposing to add a `--jtreg-failure-handler-config=<folder with config files>` to pass a folder with custom OS specific configuration files, that would be used instead of the files currently provided by the OpenJDK. This would make it easier to adapt the output to ones needs.