chore: use blessed replica to avoid changing sha256

[ghost]

There were multiple versions of the replica and ic-starter tarballs at the old URLs. The tarballs with path including /blessed/ did not change.

Also:

• disable failfast for cargo build and lint steps, since it's useful to see if a failure happened on both macos and ubuntu
• run scripts/prepare-dfx-assets.sh as a separate workflow, since other workflows run much faster by caching its output, meaning it wasn't being tested on every run.
• disable certificate.bash e2e test on linux because over the weekend, the pyparsing module on ubuntu-latest became incompatibility with mitmproxy there.