Added SMAPI crash diagnostic

[Pickysaurus]

Added a new diagnostic for Stardew Valley which will show a Critical Health Check warning if the last log generated by SMAPI is a crash log.

It works by:

1. Checking the %appdata%\StardewValley\ErrorLogs (or Linux equivalent (needs testing!))
2. Compares the last edit time of all log files.
3. A diagnostic is raised if the latest log file is SMAPI-crash.txt and it was last edited less than 12 hours ago.
4. When the latest log file is SMAPI-log.txt the diagnostic will not show.

Possible improvements:

• Detect the last time we launched the game (if possible?) and use that to work out how relevant the log is
• Localise the date/time based on the users app locale
• Add tests

[erri120]

I'm not sure what prompted this PR, whether this is just a pet project or something else. I think the only open issue related to SMAPI logs is #1721 which is about sharing logs. We had talks about a log viewer and parser before, but that got never scheduled or even written down.

Regardless of the ticket state, log parsing and diagnostics should be two separate systems. The idea behind diagnostics is to provide static analysis of the loadout and notify the user about every issue we can identify statically before they launch the game. Logs are only produced after launching the game. In the ideal world, we'd catch every issue with diagnostics before they start the game, not notify them afterwards using log parsing.

Log parsing is still helpful, especially for mod creators, and for debugging issues that can't be statically analyzed like runtime conflicts, which is why a separate system that is more fleshed out and specialized for logs would be needed. Probably a new left menu entry that opens a log viewer with a parser, a share button and many other gadgets to help work with logs. There are just too many features that we'd want in regards to logs that the diagnostic system doesn't provide because it was built for something else entirely.

I don't know what you want to do with this PR, probably fine to keep it as a draft PR for now until we figure out what we want to do for logs.