Port missing features

[nwithan8]

Description

• All features introduced into master since the rewrite process began have been ported into the rewrite.
• Improvements to client handoff
  • All EasyPostObject objects and sub-objects will be handed the client used to create them (i.e. when creating a Shipment, not only will the Shipment object have the client used to create it, assigned to it, but the sub-objects of that Shipment (ToAddress, FromAddress, Parcel, etc.) will also have the client assigned to them)
• Client equality is now determined by the client configuration (if two clients have the same API key and API base, they are equivalent)
• Beta models/services have been removed from beta folders/namespaces
  • Access to these beta features is dictated by their presence in the beta client, and beta endpoint usage is dictated by the API version override parameter in functions.
  • The namespaces/folders, while adding some organization, are ultimately unnecessary, and cause more refactoring needs when moving a feature from beta to GA

Testing

• All unit tests pass
• New unit tests have been added and recorded as needed
• EndShipper unit tests have been re-recorded for GA (no beta unit tests exist for EndShipper)

Pull Request Type

Please select the option(s) that are relevant to this PR.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Improvement (fixing a typo, updating readme, renaming a variable name, etc)

[Justintime50]

I double checked the list and this seems to be everything. Please double check yourself to ensure we haven't missed something.

[nwithan8]

I double checked the list and this seems to be everything. Please double check yourself to ensure we haven't missed something.

I have manually checked every PR made to master in the past two months, and it does seem like we have gotten everything.