[meshcop] update the DEPRECATED function mbedtls_ssl_conf_curves (#7415)

The commit updates the `mbedtls_ssl_conf_curves` with the new
alternative - `mbedtls_ssl_conf_groups`. The API has been deprecated
in `mbedtls-3.1` and will be removed in a future release. The code is
also kept backward compatible to support older versions.

.github/workflows/build.yml

@@ -134,7 +134,7 @@ jobs:
     - uses: actions/checkout@v2
       with:
         repository: ARMmbed/mbedtls
-        ref: v3.0.0
+        ref: v3.1.0
         path: third_party/mbedtls/repo
     - name: Build
       run: |