feat(sslkeylogfile): added sslkeylogfile support

[sm1thv1rus]

What changed

I added centralized SSLKEYLOGFILE support via keylog.rs, implemented in both rustls::ClientConfig for the QUIC connections and in boring2::ssl::SslContextBuilder for everything else. This enables one to log SSL / TLS secrets in the whole library by the standardized SSLKEYLOGFILE environment variable.

Type

• Bug fix
• Feature
• Refactor (no behavior change)
• Performance
• Docs / examples
• CI / tooling
• Breaking change (see "Breaking changes" below)

Related issues

Implements #42

How tested

• cargo fmt --all -- --check
• cargo clippy --workspace -- -D warnings - this failed, but only because of a needless_late_init error that appeared
• cargo clippy --workspace -- -D warnings -A clippy::needless_late_init - This succeeded instead of the above
• cargo test --workspace -- --test-threads=1 (V8 single-thread) - Importantly I added some tests to the mix so those got run here
• cargo doc --no-deps --workspace (no rustdoc warnings)
• cargo build --release --example getting_started && SSLKEYLOGFILE=./testing_sslkeylogfile.txt target/release/examples/getting_started - Importantly this one showed the creation of a valid SSLKEYLOGFILE

Breaking changes

As far as I can tell there's no breaking changes! All this does is add functionality by updating calling 2 functions, one for each of the SSL libraries.

Scope

• Use case is consistent with SCOPE.md (archival, accessibility, AI agents, security research, CTF).
• If this touches the stealth surface, the change is engineering-level (parity with a documented Chrome / Firefox behavior), not site-specific exploit code.

Checklist

• Self-reviewed
• No new warnings
• No new unsafe blocks without a // SAFETY: comment
• Public API additions have rustdoc
• Conventional-commit title