Update blst to 0.3.11 (#4624)

## Proposed Changes

This PR updates `blst` to 0.3.11, which gives us _runtime detection of CPU features_ 🎉

Although [performance benchmarks](https://gist.github.com/michaelsproul/f759fa28dfa4003962507db34b439d6c) don't show a substantial detriment to running the `portable` build vs `modern`, in order to take things slowly I propose the following roll-out strategy:

- Keep both `modern` and `portable` builds for releases/Docker images.
- Run the `portable` build on half of SigP's infrastructure to monitor for performance deficits.
- Listen out for user issues with the `portable` builds (e.g. SIGILLs from misdetected hardware).
- Make the `portable` build the default and remove the `modern` build from our release binaries & Docker images.

Author: michaelsproul

Cargo.lock

@@ -207,7 +207,7 @@ arbitrary-fuzz:
 # Runs cargo audit (Audit Cargo.lock files for crates with security vulnerabilities reported to the RustSec Advisory Database)
 audit:
 	cargo install --force cargo-audit
-	cargo audit --ignore RUSTSEC-2020-0071
+	cargo audit --ignore RUSTSEC-2020-0071 --ignore RUSTSEC-2022-0093
 
 # Runs `cargo vendor` to make sure dependencies can be vendored for packaging, reproducibility and archival purpose.
 vendor: