Debugger decorations issues

[bpringe]

Opening this to track some issues with the way debugger decorations work.

Issue 1

1. Instrument a function
2. In another namespace where the instrumented function is referenced, change the reference to make it no longer reference the function, and see that the decoration is not removed

Issue 2

1. Instrument a function
2. In another namespace, reference the function and see that the decoration is not added

Issue 3

1. Instrument a function
2. Change the function definition name and see that the references to the old function are no longer decorated, though the function definition still exists in the repl and is still instrumented
3. Calling the old function cause the debugger to start and break in the newly named function, as if it were the old one

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I'm not sure if issue 3.3 is something that can totally be "fixed" since it's somewhat a symptom of the repl that old function definitions are left around, but maybe those references to the old function, which still exists and is instrumented, should still be decorated.