Event args cancellation

[danielmarbach]

Proposed Changes

This introduces the possibility to allow the cancellation to flow into the async event handlers

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[danielmarbach]

@lukebakken I started implementing the cancellation support into the event handler wrapper. This is far from done but here is a headsup

[danielmarbach]

FYI I did not setup the commit signing on my temporary device while my main macbook is on repair. That is why some commits are not signed

[danielmarbach]

I will double-check things once more, but I guess it doesn't hurt start reviewing it

[danielmarbach]

@lukebakken do you know why AsyncEventingWrapper is a struct? Seems unnecessary because we use them as fields on objects that don't get allocated a ton. It appears to be unnecessarily complex and require comments like

// Do not make this function async! (This type is a struct that gets copied at the start of an async method => empty _handlers is copied)

for little value unless I'm missing something

[lukebakken]

I can look in the commit history. The choice of struct for the event wrappers came from a community-contributed PR, most likely from @bollhals or @stebet

I'm perfectly happy changing them to class for the reasons you stated.

[danielmarbach]

Those are two pretty smart blokes. I don't want to jump the gun ;)

[lukebakken]

FYI, I'm addressing the TODO you added around ShutdownEventArgs in a branch that depends on this one. I'm also finally fixing the directory structure so that it matches the namespaces, because that has driven me nuts for years.

[lukebakken]

Thank you yet again @danielmarbach