iskorotkov/avro: CPU Exhaustion in Avro Decoder

iskorotkov/avro is a fast Go Avro codec. Prior to 2.33.0, the Avro array and map decoders looped over an attacker-controlled block-count value without checking the underlying reader's error state inside the loop body. Reader.ReadBlockHeader returns the count as a Go int, which is 64-bit on amd64 / arm64 targets — so a producer can declare a block of up to math.MaxInt64 (~9.2 × 10¹⁸) elements followed by EOF (or any truncated payload), and the decoder will attempt that many no-op iterations before propagating the error. The realistic ceiling is "indefinite until the worker is killed externally" — a single hostile payload pins a CPU core until the process is OOM-killed, deadline-cancelled, or terminated. Remote, unauthenticated denial-of-service. This vulnerability is fixed in 2.33.0.