Rename API resource's request method

[brandur]

As seen in #928, the refresh method doesn't work for an event class.
This is because event has a field called request, and it ends up
replacing the request method that it inherited from being an API
resource, so when refresh tries to make a request, it fails because it
tries to invoke it on the accessor added for the event's property.

Here we give request a much more unique name so that it will never
conflict with a property field again, and update all internal references
to use the new name. We use alias to make the old name available for
backwards compatibility reasons because its been around for so long that
people are probably calling it.

Fixes #928.

r? @ob-stripe @richardm-stripe

[brandur-stripe]

The other thing I considered while writing this was renaming request_stripe_object to be more consistent, or try to standardize its parameters with execute_resource_request (they take the same parameters, but they're named and optional in the former and positional in the latter), but ... overall it didn't seem 100% worth it.

I do think though that in general we need to clean up a lot of the naming and modules in this library. Like, it really doesn't make too much practical sense for some request-related methods to be in the Request module and others to be in APIResource. I don't think we actually need this level of composability anywhere in practice, and it's all become pretty tightly intertwined anyway, so we should probably just flatten everything out to make it less confusing.

[brandur-stripe]

(I also have a small internal PR to reflect these changes that I'll assign to whomever ends up looking at this one.)

[richardm-stripe]

This looks good to me, happy to look at the internal PR too.

[brandur-stripe]

Thanks a lot Richard! Just assigned you the internal version as well.