Support bundles should include GZ `/var/fm` contents

[rmustacc]

Currently support bundles don't include any fault information that a system can generate. This should be included in support bundles for diagnosability and to help us correlate other issues that are going on. Specifically we should probably add /var/fm to the list of GZ-specific things to include. We should also ensure that some of the rotated FM logs are pruned periodically to ensure that we can't run a ramdisk out of space this way. While things are already in the logrotate commands, it wasn't immediately obviously to me that we ever would clean up or archive those files and not potentially fill up the ramdisk.

[davepacheco]

Just wanted to mention that if any of this work involves the sled agent DebugCollector, I've got a pretty big change there that should make this a bunch easier. (I'm not sure if that would involved in this or if the support bundle stuff will grab the files right out of /var/fm.)

[smklein]

@hawkw, @papertigers we should coordinate on this - couple things:

1. Do we want to expose an endpoint out of sled agent to "just grab all the files from /var/vm"? We have some existing endpoints for support bundles -- e.g., support_logs_download -- but the support bundle collector can nab whatever it needs. @davepacheco , if you're adding something for the DebugCollector, we could use that.
2. Mechanically adding this to the bundle (on the Nexus side) should be straightforward, because we've already gone through a similar process for zone logs (see: save_zone_log_zip_or_error in nexus/src/app/background/tasks/support_bundle/steps/host_info.rs). In that example, we used: "assemble + expose the contents of /var/fm as a zipfile which we export from the sled agent -> transfer that to Nexus -> Unzip it, re-assemble it into the support bundle".