fix(cast): accept X.509 v1 device certificates in TLS handshake

Connecting to Cast devices failed with:
Connection error: invalid peer certificate: Other(OtherError(UnsupportedCertVersion))

Many Cast devices (notably AV receivers with Chromecast built-in) serve a
self-signed X.509 version 1 certificate on port 8009. rust_cast 0.21's
NoCertificateVerification verifier accepts any certificate in
verify_server_cert, but its signature checks delegate to rustls helpers
that parse the certificate with webpki, which only supports version 3
certificates. The handshake therefore aborts for v1 device certificates;
this affects every rustls-based rust_cast release (0.19+) and only devices
happening to serve v3 certificates can connect.

Vendors rust_cast 0.21.0 under crates/vendor with a minimal patch: the
verifier's verify_tls12_signature/verify_tls13_signature now assert
validity, matching the verifier's no-validation contract and the rustls
danger verifier examples. Wired up via [patch.crates-io]; see
crates/vendor/rust_cast/QBZ_PATCH.md for the full analysis and how to drop
the patch once upstream releases the fix.

Verified against a real device serving a v1 certificate (TLS 1.2,
ECDHE-RSA-CHACHA20-POLY1305): handshake, receiver channel and heartbeat
now establish; unpatched fails at the first channel write. cargo
check/test -p qbz-cast pass (13 tests).

Refs: rustls/rustls#1298, rustls/webpki#29, #439

crates/Cargo.lock

@@ -5242,8 +5242,6 @@ dependencies = [
 [[package]]
 name = "rust_cast"
 version = "0.21.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "235d09067a35143d271fdeaf28298b4f729b5da50abdbf3b9e6395262d8bc7a9"
 dependencies = [
  "byteorder",
  "log",