Convert test vector files to pure-Rust testing modules [Python/Rust]

[brycx]

The below test modules rely on ring's testing framework to read the test vectors from files in test_data:

• other_poly1305.rs
• boringssl_chacha20_poly1305.rs
• boringssl_xchacha20_poly1305.rs

These should be converted into pure-Rust testing modules, like it has been done with the NIST CAVP HMAC test vectors. Python conversion scripts used to convert such test vector files can be found in test_generation for reference. Conversion scripts for any of the above modules are also preferred to be in Python or Rust.

[brycx]

Using ring's testing framework seems to also block testing in CI with target mips64-unknown-linux-gnuabi64.

That target has now been set to allow failure, but should be re-tested without failure, once the ring dev-dependency is gone.

[brycx]

Fixed in 47ba12d.