FileTest and Wycheproof express more-or-less the same things, so I've
just written a script to mechanically convert them. Saves writing a JSON
parser.

I've also left a TODO with other files that are worth converting. Per
Thai, the webcrypto variants of the files are just a different format
and will later be consolidated, so I've ignored those. The
curve/hash-specific ECDSA files and the combined one are intended to be
the same, so I've ignored the combined one. (Just by test counts, there
are some discrepancies, but Thai says he'll fix that and we can update
when that happens.)

Change-Id: I5fcbd5cb0e1bea32964b09fb469cb43410f53c2d
Reviewed-on: https://boringssl-review.googlesource.com/27785
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>