Handle update checker failures gracefully

[Zaxoosh]

Summary

• log update-check future failures instead of rethrowing them as runtime exceptions
• treat malformed Modrinth update responses as a failed update check instead of a client crash
• restore the interrupt flag when update-check requests are interrupted

Root Cause

#1011's log shows a timeout followed by a malformed/truncated Modrinth JSON response. The parser exception escaped through Future.get(), and checkForUpdates0 rethrew the ExecutionException as a RuntimeException, which crashed Minecraft.

Validation

• ./gradlew.bat build

Fixes #1011

[gniftygnome]

Very good. Thank you for this.

[Zaxoosh]

All good, always happy to help out!

[litetex]

So regarding #972 (comment)

Okay so I missed a few returns and exceptions in #972

I think putting a

ExecutorService executor = Executors.newThreadPerTaskExecutor(new UpdateCheckerThreadFactory());
try {
  // Do stuff
} finally {
 executor.shutdown();
}

should fix this in a much cleaner way instead of putting into every if or catch block ;)