Access the fields of `psa_key_attributes_t` directly rather than through the
`core` field. This makes the `core` field obsolete.
This commit is fully automated:
```
git ls-files '*.h' '*.c' '*.function' '*.jinja' | xargs perl -l -i -pe '$core = qr/\b(core\b|MBEDTLS_PRIVATE\(core\))/; s/->$core\./->/g; s/&(\w+)\.$core\./&$1./g; s/(\w+)\.$core/$1/g'
```
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>