Enforce that ENSURE and GUARD_OSSL use valid error codes

[lrstewart]

Description of changes:

I noticed that the same mistake made in #3853 (comment) has been made in several other places in the codebase. I corrected them all and added a check to grep_simple_mistakes.

To make the check work, I also had to correct S2N_RSA_PSS_NOT_SUPPORTED to S2N_ERR_RSA_PSS_NOT_SUPPORTED.

Testing:

This is the result if I intentionally re-introduce mistakes:

ENSURE and GUARD_OSSL require a valid error code from errors/s2n_errno.h:
/home/lrstewart/Code/s2n-tls/pq-crypto/s2n_kyber_512_evp.c:    POSIX_GUARD_OSSL(EVP_PKEY_keygen_init(kyber_pkey_ctx), S2N_FAILURE);
/home/lrstewart/Code/s2n-tls/utils/s2n_mem.c:    POSIX_ENSURE(sysconf_rc > 0, S2N_FAILURE);

FAILED Grep For Simple Mistakes check

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[WesleyRosenblum]

Do you know why POSIX_ENSURE lets you specify the error code, but POSIX_ENSURE_LTE, etc always uses S2N_ERR_SAFETY?

[lrstewart]

POSIX_ENSURE_LTE(x, y) is just a shorthand for POSIX_ENSURE(x <= y, S2N_ERR_SAFETY). If you want to specify an error other than S2N_ERR_SAFETY, you use POSIX_ENSURE.