When testing with custom entropy sources, if MBEDTLS_ENTROPY_NV_SEED
is enabled at compile time but the NV seed source is not used at
runtime, mbedtls_entropy_func makes a second pass anyway. Cope with
this in the test code by telling the entropy module not to make this
second pass.
Add a function to configure entropy sources. For testing only.
Use it to test that the library initialization fails properly if there is no
entropy source.
Allow mbedtls_psa_crypto_free to be called twice, or without a prior
call to psa_crypto_init. Keep track of the initialization state more
precisely in psa_crypto_init so that mbedtls_psa_crypto_free knows
what to do.
