Fixes for building with SP RSA small and RSA Public only

[dgarske]

Description

Fixes for building with SP RSA small and RSA Public only.

Moved some of the SP build gates into settings.h so other parts of the code can leverage them too (for example: WOLFSSL_SP_PRIME_GEN).

ZD 18996

Testing

./configure --prefix=$PWD/../wolf-install CFLAGS="-DWOLFSSL_SP_SMALL -DUSE_SLOW_SHA256 -DNO_SIG_WRAPPER -DNO_AES_192 -DNO_AES_256 -DWOLFSSL_RSA_PUBLIC_ONLY -DNO_CHECK_PRIVATE_KEY  -DNO_FILESYSTEM -DWOLFSSL_PUBLIC_MP -DWOLFSSL_NO_MALLOC -DWOLFSSL_SP_NO_MALLOC -DNO_ASN_TIME  -DIGNORE_NAME_CONSTRAINTS  -ffunction-sections -fdata-sections -fno-builtin" --enable-cryptonly --enable-aescfb --enable-rsapss --disable-pkcs8 --disable-pkcs11 --disable-pkcs12 --disable-dh --disable-errorstrings --disable-poly1305 --disable-chacha --disable-sha --disable-sha224 --disable-sha512 --disable-sha3 --disable-md5 --disable-aescbc --disable-aesgcm --disable-aesccm --disable-oldnames --disable-coding --disable-inline --disable-memory --disable-harden --disable-asm --disable-errorqueue --disable-error-queue-per-thread --disable-tls13 --disable-tlsv12 --disable-tlsv10 --disable-optflags --disable-memory --disable-oldtls --disable-filesystem --enable-singlethreaded --enable-static --disable-shared --enable-sp=smallrsa2048
make
make install
./wolfcrypt/test/testwolfcrypt

Checklist

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

[dgarske]

Retest this please: "Known configs failed on: FAIL: scripts/external

WOLFSSL_EXTERNAL_TEST set, running test...
PING k.sni.global.fastly.net (151.101.2.137) 56(84) bytes of data.
64 bytes from 151.101.2.137 (151.101.2.137): icmp_seq=1 ttl=63 time=3.21 ms
64 bytes from 151.101.2.137 (151.101.2.137): icmp_seq=2 ttl=63 time=1.93 ms
--- k.sni.global.fastly.net ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 1.932/2.572/3.212/0.640 ms
SSL_read reply error -397, Peer closed underlying transport Error
wolfSSL error: SSL_read failed
SSL version is TLSv1.2
SSL cipher suite is TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
SSL curve name is SECP256R1
SSL connect ok, sending GET...
Client connection failed
FAIL scripts/external.test (exit status: 1)