recovery: retransmit blocked frames after loss

[xgame92]

Summary

• retransmit lost DATA_BLOCKED frames while the connection remains blocked at the same limit
• retransmit lost STREAM_DATA_BLOCKED frames while the stream remains active and blocked at the same limit
• suppress stale retransmissions after flow-control increases, local write shutdown, or peer STOP_SENDING
• cover Cubic and BBR2 with receiver-observable ACK-loss tests

Testing

• cargo +nightly fmt -- --check
• cargo clippy --release --features=async,ffi,qlog --workspace -- -D warnings
• cargo test --release --all-targets --features=async,ffi,qlog --workspace
• cargo test --release --doc --features=async,ffi,qlog --workspace

Fixes #2644