Extend "Code Intentions": Event handler generation

[GhostInTheSteiner]

The code intentions for Consulo don't live up to their counterparts in other Jetbrains Products such as Rider. Those are all options (even though more intentions apparently work):

This is just a one-person project for the most part, so I'll restrict myself to a few intentions that are still lacking and that I personally consider important.

Create handler method intention

Only lambdas and delegates are possible. Also allow the generation of an actual handler method like in Visual Studio: