Improve type bounds for `ScopeExtractor`

[ndr-brt]

Feature Request

Now that we have a PolicyContext hierarchy, in ScopeExtractor the policy context parameter could be bound to RequestPolicyContext as it's only used in that context.

Which Areas Would Be Affected?

e.g., DPF, CI, build, transfer, etc.

Why Is the Feature Desired?

improve adopter experience

Solution Proposal

If possible, provide a (brief!) solution proposal.