Update AASM DSL generator

[davebenvenuti]

Motivation

Hello! I encountered some type errors in a project related to the AASM gem. More specifically, it appears the DSL generator for AASM only supports one form of their lifecycle callbacks.

class Foo
  include AASM
  
  aasm do
    state :state1
    state :state2

    event :do_something do
      transitions from: :state1, to: :state2

      after :some_method
    end

    def some_method
    end
  end
end

The above code would produce a typeerror along the lines of after requires a block parameter, but no block was passed https://srb.help/7021. However, this is in fact valid usage of the after hook. Similar to ActiveRecord callbacks, they accept either a block or a symbol corresponding to a method name.

Implementation

This PR updates the generated sigs for AASM lifecycle hooks from this:

sig { params(block: T.proc.bind(StateMachine).void).returns(T.untyped)  }

To this:

sig { params(symbol: T.nilable(Symbol), block: T.nilable(T.proc.bind(StateMachine).void)).returns(T.untyped) }  }

Tests

I updated the relevant test.

[kddnewton]

Looks legit to me