Add shared_context for protected ref access specs

What does this MR do and why?

Add shared_context for protected ref access specs

All of our protected ref access spec have very similar configurations. This change extracts the common objects into a shared context.

The association was previously passed to the shared_examples but this new shared_context can find the correct association without needing to pass it so we no longer need to pass :protected_branch or :protected_tag when including the examples into a spec.

A number of duplicated variables have been removed.

We were previously including shared_examples with include_examples. However, include_examples leaks state which was causing these specs to interact with each other. This was only evident after adding the shared_context. We have now switched to using it_behaves_like which wraps the examples in a context block, isolating the state from the parent spec.

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