Per BoringSSL's FIPS policy, its `main` branch is the "update branch"
for FedRAMP compliance's purposes.
This means that we can stop using a specific BoringSSL branch when
enabling FIPS, as well as a number of hacks that allowed us to build
more recent BoringSSL versions with an older pre-compiled FIPS modules.
This also required slightly updating the main BoringSSL submodule, as
the previous version had an issue when building with the FIPS option
enabled. This is turn required some changes to the PQ patch as well as
some APIs that don't seem to be exposed publicly, as well as changing
some paths in the other patches.
In order to allow a smooth upgrade of internal projects, the `fips-compat`
feature is reduced in scope and renamed to `legacy-compat-deprecated` so
that we can incrementally upgrade internal BoringSSL forks. In practice
this shouldn't really be something anyone else would need, since in
order to work it requires a specific mix of BoringSSL version and
backported patches.
Fix three potential timing sidechannels. These don't affect ephemeral
usage of Kyber as in TLS, but it's good practice to get rid of them anyway.
Also adds IPDWing, a preliminary version of X-Wing using the initial public
draft (IPD) of ML-KEM. Don't use it.
Alessandro Ghedini