Asyncify verbose option

[kripken]

This logs out the decisions made about instrumenting functions, which
can help figure out why a function is instrumented, or to get a list of
what might need to be.

As the test shows, it can print things like this:

[asyncify] import is an import that can change the state
[asyncify] calls-import can change the state due to import
[asyncify] calls-calls-import can change the state due to calls-import
[asyncify] calls-calls-calls-import can change the state due to calls-calls-import

(the test has calls-calls-calls-import => calls-calls-import => calls-import -> import).

Not sure how useful this might be, but it was easy to write up. Thoughts?

cc @curiousdannii @aardappel

[aheejin]

Is looks possible for some functions to be logged as added as can-change-state functions but if the only-list is present, they are eventually ignored silently, i.e., without any other log messages that they are ignored, right? Would it be better to check the only list when logging for other causes..?

[kripken]

I think this log message here would be shown, though, so it's not completely silent? This message would say they are set to false, which overrides the previous messages.

[aheejin]

Ah you're right. Sorry I thought this is only printed when the value is true.

[aardappel]

Yes, the "due to" will be super useful in tracking down why a function that doesn't appear necessary is included, thanks!