Some files were named 𝑥_test.txt and some 𝑥_tests.txt. This change
unifies around the latter.

Change-Id: Id6f29bad8b998f3c3466655097ef593f7f18f82f
Reviewed-on: https://boringssl-review.googlesource.com/8150
Reviewed-by: David Benjamin <davidben@google.com>

This commit adds coverage of the "offer" (first) step, as well as
testing all outputs of the "accept" (second) step, not just the shared
key.

Change-Id: Id11fe24029abc302442484a6c01fa496a1578b3a
Reviewed-on: https://boringssl-review.googlesource.com/8100
Reviewed-by: Adam Langley <agl@google.com>

The test vectors are taken from the reference implementation, modified
to output the results of its random-number generator, and the results of
key generation prior to SHA3.  This allows the interoperability of the
two implementations to be tested somewhat.

To accomplish the testing, this commit creates a new, lower-level API
that leaves the generation of random numbers and all wire encoding and
decoding up to the caller.

Change-Id: Ifae3517696dde4be4a0b7c1998bdefb789bac599
Reviewed-on: https://boringssl-review.googlesource.com/8070
Reviewed-by: Adam Langley <agl@google.com>