WIP: opt-in rustls-ffi FIPS support

[cpu]

FIPS feature

Using make FIPS=true with the Makefiles, or cmake -DFIPS="true" -S . -B build with the Windows cmake build will activate the aws-lc-rs feature of rustls-ffi, and the rustls/fips feature of Rustls.

On MacOS and Windows this requires some additional build tooling (Golang and Ninja). See the rustls manual and the aws-lc-rs-fips-sys crate for more information.

API additions

• Ability to instantiate the FIPS default crypto_provider using a new function rustls_default_fips_provider(), available only when the fips feature is activated.

• Ability to determine if a given crypto_provider is in FIPS mode using a new function rustls_crypto_provider_fips().

• Ability to determine if a given rustls_client_config would create connections that are FIPS compatible with a new function
  rustls_client_config_fips().

• Ability to determine if a given rustls_server_config would create connections that are FIPS compatible with a new function
  rustls_server_config_fips().

• Ability to determine if a given rustls_connection was created from a rustls_client_config that was FIPS enabled with a new function rustls_connection_fips(). Doing equivalent for a server connection is not presently supported upstream (see consistent APIs for connection FIPS indicator rustls#2174).

TODO

• presently the Mac and Windows FIPS-enabled builds fail with unresolved symbol errors when building the client/server examples
• there's no FIPS specific integration tests.

[cpu]

update rustls 0.23.13 -> 0.23.15

Pulling this out into a separate PR since I have some TODOs for this one: #479

[cpu]

presently the Mac and Windows FIPS-enabled builds fail with unresolved symbol errors when building the client/server examples

The Ubuntu FIPS CI works great, and so do my local test builds on x86_64-unknown-linux.

Both MacOS and Windows build the Rust rustls-ffi lib and the aws-lc-rs/aws-lc-sys-fips crates without error, but fail to build/link the example C programs:

The MacOS builds fail to compile the client/server example .c programs with errors like:

cc -o target/client target/client.o target/common.o target/release/librustls_ffi.a -Wl,-dead_strip -framework Security -framework Foundation
Undefined symbols for architecture arm64:
  "_aws_lc_fips_0_12_13_AES_ecb_encrypt", referenced from:
      rustls::crypto::aws_lc_rs::quic::HeaderProtectionKey::xor_in_place::h57084e5b13308bb1 in librustls_ffi.a[72](rustls-c38d2f20cf176c7d.rustls.1215cb8b128a8c54-cgu.12.rcgu.o)

Similar failures for the cmake builds on Windows:

  Generating Code...
rustls_ffi.lib(rustls-c4ef5bb999bbcf41.rustls.dd57a86e5d66d92f-cgu.08.rcgu.o) : error LNK2001: unresolved external symbol aws_lc_fips_0_12_13_EVP_PKEY_free [D:\a\rustls-ffi\rustls-ffi\build\tests\client.vcxproj]

Probably missing some extra linker arguments for the C programs (?) - have to put a pin in this for today but will debug further when time permits.