Move Mbed TLS self tests to a separate configuration ...

We potentially save flash space by not enabling Mbed TLS self-tests
by default. A new test config file, TESTS/configs/mbedtls.json, is
provided to enable self tests. This newly created JSON file also
enables timing in Mbed TLS so timing gets tested.

mbedtls: Run mbedtls_timing_self_test if MBEDTLS_TIMING_C ...

This allows us to verify the support for Mbed TLS timing on Mbed OS.

Note: The macros MBEDTLS_TIMING_C and MBEDTLS_TIMING_ALT are not
enabled by default and need to be additionally enabled to run this
test.

CMake: rename greentea test macro

CMake: Add support for Mbed TLS Greentea tests ...

The Mbed TLS Greentea tests can now be built with CMake.

tests: Limit PSA crypto tests to Arm-v7M targets ...

The PSA crypto tests in
connectivity/mbedtls/tests/TESTS/mbedtls/sanity/main.cpp are only
supported for Arm-v7M PSA targets. For Arm-v8M PSA targets, crypto
regression tests provided by TF-M are used. Refer to
https://github.com/ARMmbed/mbed-os-tf-m-regression-tests for more
information.

Signed-off-by: Devaraj Ranganna <devaraj.ranganna@arm.com>

tests: Fix test_crypto_asymmetric_encrypt_decrypt ...

The test `test_crypto_asymmetric_encrypt_decrypt` was incorrectly
setting the key usage flags. The key usage is updated to support both
encryption and decryption.

Signed-off-by: Devaraj Ranganna <devaraj.ranganna@arm.com>

Move mbedtls greentea tests