[TODO] Update for CI checking script in OP-TEE

The CI in the OP-TEE repo runs an expect script to test Rust examples. Originally, this script was located at `teaclave-trustzone-sdk/ci/qemu-check.exp` but has been duplicated to `OP-TEE/build/rust.exp` in https://github.com/OP-TEE/build/pull/717 and maintained in OP-TEE repo.

However, `rust.exp` needs to be updated to include checks for additional `no_std` examples: `tcp_client` and `udp_client`.

Before adding these checks, we should first enable IPv6 support in QEMU, as discussed
in https://github.com/apache/incubator-teaclave-trustzone-sdk/pull/164#discussion_r1928165412, to properly test the `tcp_client` example.

Leaving a TODO here as a record.

Start with OP-TEE/build/rust.exp and the existing checks for Rust examples. Read the linked discussion about enabling IPv6 support in QEMU before adding checks for the tcp_client and udp_client no_std examples. Done means IPv6 is enabled and both examples are covered by the CI script.

Written by the indexing model from the issue text.