Remove "name()" from StateBuilder interface

[jtfmumm]

We don't currently use the StateBuilder name for any
reason and it creates more boilerplate when creating
stateful apps. This removes name() from the interface
and updates Python and Go APIs as well as example
apps and book examples accordingly. Instead of the
StateBuilder name, we now use the state partition
name, which would do the trick if we ever end up
needing it for logging purposes.

Closes #1809

[jtfmumm]

@aturley I've put you on this PR because it's mostly changes to the Python and Go APIs as well as related examples. The core changes are removing name() from the StateBuilder interface and using the state partition name where we'd previously used that method internally.

[SeanTAllen]

Given that this is completely invisible to end users, I think the CHANGELOG label can be removed. There's no need for this to be in the CHANGELOG.

[jtfmumm]

@SeanTAllen This required changes to the Go and Pony example apps since it removed the requirement for name(). That's not invisible. Note that @aturley included that method in his latest blog post on the Go API since it was a requirement. Of course, the example apps would have still compiled since this reduces the requirements for the interface, but it's no longer necessary and serves no purpose to implement that method after this change.

[SeanTAllen]

Ah, ok. This is however, a non-breaking change, correct?

I'm looking at https://github.com/WallarooLabs/wallaroo/blob/428949bec59d7682919ddd8a66bf0a6c477ca78d/book/python/writing-your-own-partitioned-stateful-application.md

and it seems to have not been updated for the new API.

[jtfmumm]

@SeanTAllen This is a non-breaking change. I don't see what I missed in that document you linked to.

[aturley]

Looks good to me.