Support FIPS-capable TLS by `aws-lc-rs`

Motivation

libsql’s HTTP/TLS stack is built on rustls + hyper-rustls. Today that path is effectively ring-backed, which blocks deployments that need FIPS-validated cryptography.

The Rust TLS ecosystem has been moving toward aws-lc-rs for this reason:

• rustls made aws-lc-rs the default crypto backend and added FIPS support
• rustls documents a FIPS path via aws-lc-rs (fips feature + FIPS CryptoProvider) — see rustls FIPS guide
• aws-lc-rs exists in large part as a ring-compatible provider with FIPS

Supporting aws-lc-rs (and ideally a documented FIPS configuration) would align libsql with that direction and unblock regulated / government workloads.

Proposal

• Expose a crate feature (e.g. aws-lc-rs) that backs the built-in TLS connector with aws-lc-rs

I am happy to contribute a PR for this proposal if needed.

Alternatives

• Hard switch from ring to aws-lc-rs, but this may introduce more breaking changes