Race on Terminal.interceptors

[mikehearn]

Terminal.interceptors should only be modified whilst holding Terminal.lock but the lock isn't taken in Terminal.addInterceptor or Terminal.removeInterceptor.

I had a quick go at fixing this but you can't use synchronized() in non-JVM code. Actually I'm not sure how you're meant to do locking like this in MPP code.

Exception in thread "Thread-0" java.util.ConcurrentModificationException
        at java.base/java.util.ArrayList$Itr.checkForComodification(ArrayList.java:1013)
        at java.base/java.util.ArrayList$Itr.next(ArrayList.java:967)
        at com.github.ajalt.mordant.internal.MppImplKt.sendInterceptedPrintRequest(MppImpl.kt:160)
        at com.github.ajalt.mordant.terminal.Terminal.sendPrintRequest(Terminal.kt:269)
        at com.github.ajalt.mordant.terminal.Terminal.rawPrint(Terminal.kt:265)
        at com.github.ajalt.mordant.terminal.Terminal.print(Terminal.kt:194)
        at com.github.ajalt.mordant.terminal.PrintTerminalCursor.show(TerminalCursor.kt:158)
        at com.github.ajalt.mordant.internal.JvmTerminalCursor.show(MppImpl.kt:113)
        at hydraulic.factory.progress.FancyTerminalParallelProgressTracker.close(FancyTerminalParallelProgressTracker.kt:390)
        at hydraulic.factory.progress.FancyTerminalParallelProgressTracker.shutdownHook$lambda-0(FancyTerminalParallelProgressTracker.kt:46)
        at java.base/java.lang.Thread.run(Thread.java:833)