Refactor the middleware setup [starts v7 breaking changes]

[fselmo]

What was wrong?

In order to process requests and responses separately and to eventually support batch requests, we need to uncouple the make_request() method from being sandwiched along with all the middleware in each request. If we want APIs that can process request params separately from making a request, we need to refactor quite a bit of the code to massage this sort of logic in.

How was it fixed?

In this PR I am refactoring the middleware from the functional programming paradigm of a sandwiched request into a class-based structure with request processors and response processors. The ultimate end result for most requests is these classes still wrap the make_request, as it is often convenient to be able to replace the make_request function in order for a specific request to not be made under certain conditions some middleware necessitate (currently this is only true for the local_filter_middleware).

Imo this class-based structure makes the middleware a bit easier to read and create. If a middleware only processes request, it only needs to define a request processor; if the response is the only thing the middleware touches, it can override the response processor on the class, etc. In case the make_request method itself needs to be altered, the _wrap_make_request() method can be overridden and that would behave similarly to the way the middlewares currently work.

Some things to note:

• This refactor removes the request retry middleware from the provider and removes the concept of provider middleware altogether. Instead, exception retry logic is done as a configuration on the HTTP providers.
• This refactor removes the result generator middlewares and opts for a request_mocker fixture for dealing with mocked requests. This has proved to be quite nice to work with, at least for the current tests, and it removes the need to create, inject, and clean up middleware for each test. Instead, the context manager takes care of mocking while inside the manager and cleaning up when exiting the context manager for both sync and async.
• The simple_cache_middleware is moved to a decorator on the make_request method for the providers. This can be turned on and configured as configurations on the appropriate provider classes.

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• closes Remove reliance on web3 instance for name_to_address_middleware #3021 - Removes the need to pass w3 into the default middlewares
• closes Remove ABI Middleware #2995 - Remove the need for abi_middleware by fixing where the name_to_address middleware would override request formatters
• closes Improve user experience around provider-specific middlewares #2990 - Removes provider-specific middleware except for a hardcoded specific set of middleware for the in-house EthereumTesterProvider
• closes rename geth_poa_middleware to something more generic #899 - The current version of the middleware takes extraData field and changes it to proofOfAuthority. The name was changed from geth_poa_middleware to extradata_to_poa_middleware

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Todo:

• Add entry to the release notes
• Revise some of the type hinting. In particular the type hinting around the Middleware within manager and provider classes
• Update documentation to reflect above changes ( will be in a separate PR)

Cute Animal Picture

[pacrob]

Nicely done! 🏋️
GTG for me.

[kclowes]

Left a few nits to take or leave, but looks good!

[fselmo]

@kclowes I think I addressed all your comments. Let me know if there's anything else outstanding and how you feel about the tupleization commit.

[kclowes]

LGTM! 🚀