Previously it was disabled as too experimental, which no longer holds. Also,
this option introduces new APIs, so it's not only about an internal
alternative (as the comment in config.pl used to state) - people who request a
full config should get all of the available APIs.
Adapt all.sh: now all builds with full config will also test this option, and
builds with the default config will test without it. Just to be sure, let's
have a build with full config minus this option.
Update documentation of MBEDTLS_USE_PSA_CRYPTO to reflect the status of the
new APIs it enables in Mbed TLS and why they're still opt-in.
971dea3745