Ignore exceptions thrown from Thread.UncaughtExceptionHandler

[dkhalanskyjb]

Fixes #4516

Background

Whenever an uncaught exception happens in a coroutine, it gets reported to the CoroutineExceptionHandler. See https://kotlinlang.org/docs/exception-handling.html#coroutineexceptionhandler. However, if it's not installed, a platform-specific handler is used.
On the JVM, this means invoking the thread's
UncaughtExceptionHandler, which logs the exception to the console by default, but can be configured to do other things (for example, on Android, it will crash the application).

Problem

User-specified UncaughtExceptionHandler instances are allowed to throw exceptions.
Java's documentation says so
(https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/Thread.UncaughtExceptionHandler.html):

Any exception thrown by this method will be ignored by the Java Virtual Machine.

This means a user is allowed to write a throwing
UncaughtExceptionHandler, and the caller has to deal with it.

In our implementation, however, we are simply invoking the exception handler as a plain function, and if that function throws an exception, we allow this exception to propagate to the coroutine machinery, causing it to fail.

Solution

To comply with the contract defined for UncaughtExceptionHandler, we also ignore the exceptions thrown from there.

[qwwdfsad]

you can add something like val _ = "Welcome, weary traveler. To my breakpoint place" which is both self-explanatory and funny (okay, maybe only self-explanatory)