Don't dispose timers if we're in our UnhandledException handler.#104829

StephenMolloy wants to merge 3 commits intodotnet:release/6.0-stagingdotnet/runtime:release/6.0-stagingfrom

StephenMolloy:bp6_64115_Memcache-UnhandledEx-Timer-DeadlockStephenMolloy/runtime:bp6_64115_Memcache-UnhandledEx-Timer-DeadlockCopy head branch name to clipboard