Fix parsing RPK with no parameters.

[kareem-wolfssl]

Description

Fixes zd#19911

Fix parsing RPK with no parameters. As per RFC7250 section 3, the algorithm parameters are optional.

Fix building unit tests with --enable-rpk --disable-rsa.

Testing

Customer provided test key.

The following configure line was used for building unit tests:

./configure --enable-kyber --enable-mlkem --enable-dilithium --enable-dtls --enable-dtls13 --enable-dtls-frag-ch --enable-debug --enable-debug-trace-errcodes \
CFLAGS="-DHAVE_RPK -DWOLFSSL_DER_LOAD -DWOLFSSL_LOGGINGENABLED_DEFAULT=1" --disable-rsa

Checklist

• [ ] added tests
• [ ] updated/added doxygen
• [ ] updated appropriate READMEs
• [ ] Updated manual and documentation