Verify TLS handshake signatures with --insecure

[ryanfowler]

Summary

• share one insecure rustls server verifier across transport and TLS inspection
• keep certificate validation permissive while validating TLS 1.2 and TLS 1.3 CertificateVerify signatures with provider algorithms
• test self-signed acceptance and invalid handshake signature rejection in transport and inspection

Checks

• cargo fmt --check
• cargo clippy --locked --all-targets --all-features -- -D warnings
• cargo test --locked --all-features --lib --bins
• cargo test --locked --all-features --test cli --test formatting --test grpc --test har --test http --test install --test network --test terminal --test update --test websocket -- --test-threads=2