Fix RNG issue with Intel RD and cleanup to remove old ARC4 support

[dgarske]

Fix RNG issue with Intel RDRAND and RDSEED accelerations not being used because HAVE_HASHDRBG was always being defined if !WOLFSSL_FORCE_RC4_DRBG. Added new --enable-intelrand option to indicate use of RDRAND preference for RNG source (if RDRAND not supported by CPU then HASHDRBG will be used). The --enable-intelasm option enables the RDSEED support for seeding HASHDRBG if CPU supports it. Allow use of seed as RNG source if --disable-hashdbrg (shows build warning). Cleanup to remove old ARC4 RNG support. Fixed random_test return code with !HAVE_HASHDRBG. Cleanup of ./configure --help alignment.

[toddouska]

rdseed should not be used as PRNG, it should only be used to seed an PRNG.

Was rdseed tested?

[dgarske]

The RDSEED is only used to seed the PRNG. RDRAND can be used with --enable-intelrand as the RNG source with DRBG as backup. I tested RDSEED on the SGX machine and it is used with --enable-intelasm. Also tested with --enable-intelrand and the RDSEED was not used, but RDRAND was used.

[toddouska]

This still needs a little work.

1. Using GenerateSeed() as GenerateBlock() backup isn't good. Some of the seeds aren't suitable (in speed or stirring) for this output.

2. --disable-hashdrbg is still using hashdrbg at build time

3. --enable-intelrand --disable-hashdrbg still builds (probably because of 1 and 2). I think CUSTOM rand generate block should be required in this case for a suitable backup.

[dgarske]

@toddouska : Thanks of the review.

1. Using generate seed as backup only occurs if HASHDRBG is disabled and produces a build #warning. This was an idea I had for supporting Whitewood and other future good RNG seed sources. My thought was the compiling warning was sufficient to indicate issue.

2. To maintain comparability with existing functionality the only way to actually disable the HASHDBRG is to also have CUSTOM_RAND_GENERATE_BLOCK defined.
   See random.h line 50: https://github.com/wolfSSL/wolfssl/pull/805/files#diff-e78474b4037227cbca46c247ec6779e1R50

3. Yes it builds and works because HASHDRBG is still enabled unless CUSTOM_RAND_GENERATE_BLOCK is defined.

[toddouska]

Thanks.