Rather than adding a new mode to EVP_PKEY_CTX, upstream chose to tie
single-shot signing to EVP_MD_CTX, adding functions which combine
EVP_Digest*Update and EVP_Digest*Final. This adds a weird vestigial
EVP_MD_CTX and makes the signing digest parameter non-uniform, slightly
complicating things. But it means APIs like X509_sign_ctx can work
without modification.

Align with upstream's APIs. This required a bit of fiddling around
evp_test.cc. For consistency and to avoid baking details of parameter
input order, I made it eagerly read all inputs before calling
SetupContext. Otherwise which attributes are present depend a lot on the
shape of the API we use---notably the NO_DEFAULT_DIGEST tests for RSA
switch to failing before consuming an input, which is odd.

(This only matters because we have some tests which expect the operation
to abort the operation early with parameter errors and match against
Error. Those probably should not use FileTest to begin with, but I'll
tease that apart a later time.)

Upstream also named NID_Ed25519 as NID_ED25519, even though the
algorithm is normally stylized as "Ed25519". Switch it to match.

Change-Id: Id6c8f5715930038e754de50338924d044e908045
Reviewed-on: https://boringssl-review.googlesource.com/17044
Commit-Queue: Steven Valdez <svaldez@google.com>
Reviewed-by: Steven Valdez <svaldez@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>

BUG=187

Change-Id: I5775ce0886041b0c12174a7d665f3af1e8bce511
Reviewed-on: https://boringssl-review.googlesource.com/14505
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>

All the signature algorithm logic depends on X509_ALGOR. This also
removes the X509_ALGOR-based EVP functions which are no longer used
externally. I think those APIs were a mistake on my part. The use in
Chromium was unnecessary (and has since been removed anyway). The new
X.509 stack will want to process the signatureAlgorithm itself to be
able to enforce policies on it.

This also moves the RSA_PSS_PARAMS bits to crypto/x509 from crypto/rsa.
That struct is also tied to crypto/x509. Any new RSA-PSS code would
have to use something else anyway.

BUG=499653

Change-Id: I6c4b4573b2800a2e0f863d35df94d048864b7c41
Reviewed-on: https://boringssl-review.googlesource.com/7025
Reviewed-by: Adam Langley <agl@google.com>