ECDH: Adapt tests for mbedtls_ecdh_setup()
The recently added `mbedtls_ecdh_setup()` function is not used in the
tests yet. This commit adapts the tests to the new workflow.
Having done that, the old lifecycle is not tested anymore, so we add a
new test to ensure backward compatibility.
diff --git a/tests/suites/test_suite_ecdh.data b/tests/suites/test_suite_ecdh.data
index 0165a7e..89e5e3a 100644
--- a/tests/suites/test_suite_ecdh.data
+++ b/tests/suites/test_suite_ecdh.data
@@ -69,3 +69,7 @@
ECDH restartable rfc 5903 p256 restart disabled max_ops=250
depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
ecdh_restart:MBEDTLS_ECP_DP_SECP256R1:"C88F01F510D9AC3F70A292DAA2316DE544E9AAB8AFE84049C62A9C57862D1433":"C6EF9C5D78AE012A011164ACB397CE2088685D8F06BF9BE0B283AB46476BEE53":"D6840F6B42F6EDAFD13116E0E12565202FEF8E9ECE7DCE03812464D04B9442DE":0:250:0:0
+
+ECDH exchange legacy context
+depends_on:MBEDTLS_ECP_DP_SECP192R1_ENABLED
+ecdh_exchange_legacy:MBEDTLS_ECP_DP_SECP192R1