refactor: update all callers to new NewConfig signature

[meling]

Part of #294.

Summary

Update every call site in the codebase that used the old NewManager + NewConfiguration two-step pattern (or srv.NewConfig) to use the new gorums.NewConfig(nodes, dialOptions...) API.

Changes

• config_test.go: replace NewManager / NewConfiguration with NewConfig; use cfg.Close() for teardown
• server_test.go: replace srv.NewConfig(...) with gorums.NewConfig(..., gorums.WithServer(srv))
• inbound_manager_test.go: update to NewConfig
• testing_shared.go: update TestConfiguration to call NewConfig with withManager option
• testing_bufconn.go: add bufconnDialOption helper; update getOrCreateManager
• testopts.go: introduce managerRef type and update WithManager to take a Configuration instead of *Manager
• examples/storage/client.go: replace two-step setup with proto.NewConfig; add cfg.Close()
• examples/storage/repl.go: remove mgr field from repl; access nodes via cfg.Nodes()
• cmd/benchmark/main.go: replace benchmark.NewManager / benchmark.NewConfiguration with benchmark.NewConfig; add cfg.Close()
• internal/tests/config/config_test.go: update to new API

Files Changed

config_test.go, server_test.go, inbound_manager_test.go, testing_shared.go, testing_bufconn.go, testopts.go,
examples/storage/client.go, examples/storage/repl.go, cmd/benchmark/main.go, internal/tests/config/config_test.go