Add a rule to discourage use of T::Struct#serialize

[glortho]

As the Sorbet docs themselves admit, T::Struct#serialize has some surprising behavior, such that it is often better to implement serialization by hand.

To avoid these issues, it would be nice to have a rule that disallows T::Struct#serialize. Ideally it would include these additional features:

• It should link to the Sorbet docs that explain why we're make this recommendation
• It should link to an example of the preferred pattern
• It should respect an allowlist of exceptions
• It should not discourage use of T::Enum#serialize (which is safer)

I'm happy to contribute an implementation for review, but I'd love to hear any feedback about this approach in the meantime!

[sambostock]

I think this would be challenging, because RuboCop has no knowledge of what the type of an object is. Given

object.serialize

or even something more explicit like

MyStruct.new(key: value).serialize

there would be no way for it to know if the receiver is a T::Struct, T::Enum, or some other object.

[andyw8]

Maybe there is a way: #142