fix!: match the backend's standardized single-level pagination shape

[lakhansamani]

Summary

The Authorizer backend removed the PaginatedRequest wrapper type entirely (see the corresponding authorizerdev/authorizer PR — a fix(graphql)! breaking-change commit standardizing GraphQL pagination on PaginationRequest directly, matching the proto/gRPC surface, which never had a double-wrapper in the first place).

• ListClientsRequest/ListTrustedIssuersRequest/ListSAMLServiceProvidersRequest/ListOrganizationsRequest/ListOrgMembersRequest/ListOrgDomainsRequest: their pagination field was typed PaginatedRequest (itself wrapping PaginationRequest) — now PaginationRequest directly. Breaking change for callers constructing these with a nested pagination=.
• verification_requests/webhooks/email_templates (both AuthorizerAdminClient and AsyncAuthorizerAdminClient): took PaginatedRequest as their whole request parameter and hardcoded $data: PaginatedRequest in the GraphQL query strings — now take PaginationRequest directly, $data: PaginationRequest.
• _proto.py's build_message(): removed a dead-code-now branch that specifically detected and collapsed the double-nested {"pagination": {"pagination": {...}}} shape for REST/gRPC callers — unreachable once no caller can produce that shape anymore.
• PaginatedRequest is no longer exported from the package.

Also fixed 5 pre-existing bugs in tests/integration/test_live.py uncovered while making this change: two test_admin_users/test_async_admin_users calls were passing t.PaginatedRequest(...) where admin.users()/c.users() actually expect t.ListUsersRequest — a type mismatch unrelated to this fix that happened to go unnoticed until PaginatedRequest was removed and the test file could no longer even construct it.

Test plan

• mypy src/ and ruff check src/ tests/ clean
• pytest tests/ --ignore=tests/integration — 112 unit tests pass
• Verified against a locally built authorizer image running the backend fix (not yet released): all 63 live integration tests pass across all three transports (graphql, rest, grpc), including the pagination-related suite (test_admin_users, test_admin_verification_requests, test_admin_webhook_lifecycle, test_async_admin_users)

Please coordinate merging/releasing this alongside the backend fix — until the backend PR ships, this SDK version would send a shape the currently-deployed backend rejects.