crypto/internal/fips140test: add ML-KEM ACVP tests

crypto/internal/fips140test: add ML-KEM ACVP tests

Adds ACVP test coverage for ML-KEM based on the NIST spec:

  https://pages.nist.gov/ACVP/draft-celi-acvp-ml-kem.html

Notably we need to update the BoringSSL module version because the
acvptool was only recently updated to support testing ML-KEM.

A few non-test updates are also required for the
crypto/internal/fips140/mlkem package:

* For keyGen tests a new ExpandedBytes768() function is added that
  converts a DecapsualtionKey768 struct into the expanded NIST
  serialization. The existing Bytes() function returns the
  key's seed, while ACVP testing requires the more cumbersome format.
* For decap tests a new TestingOnlyNewDecapsulationKey768()
  constructor is added to produce a DecapsulationKey768 struct from the
  expanded FIPS 203 serialization provided by the ACVP test vector. The
  pre-existing NewDecapsulationKey768() function expects a seed as
  input.

The generate1024.go helper is updated to translate the above changes to
the generated mlkem1024.go implementation.

Both of these new functions are exclusively for ACVP usage and so not
present in the public mlkem API. End users should always prefer to work
with seeds.

Updates #69642

Change-Id: I79784f8a8db00a2ddefdcece4b8de50b033c8f69
Reviewed-on: https://go-review.googlesource.com/c/go/+/637439
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>