Fix CID handling for single-path H3 clients - #910

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Thank you for submitting this PR and investigating the CID interoperability issue!

Could you please open an issue first describing the observed problem and the relevant RFC requirement? The current change marks the peer’s handshake SCID as original, excluding it from active_connection_id_limit. This conflicts with [RFC 9000 §18.2](https://www.rfc-editor.org/rfc/rfc9000.html#section-18.2), which requires the handshake CID to count toward the limit.

If the goal is only to support peers providing more than eight CIDs, please rebase on main, preserve the existing CID-accounting logic, and change only the limit. The unrelated xqc_conn_try_add_new_conn_id() behavior change need to be removed unless separately justified.