Add fuzz tests for LZ4FrameInputStream and LZ4BlockInputStream #122

The Jazzer suite (src/test/net/jpountz/fuzz/) covers the block compressors, block decompressors and XXHash, but not the stream classes, which is where recent bugs have been found.

Following .clinerules/coding.md:

• one @FuzzTest per stream class, decompressor and flag combination, each with its own <execution> in the fuzz profile;
• a fixed op prefix, then consumeRemainingAsBytes();
• raw input with no round-trip.

Rules for the targets:

• Mix read(), read(byte[]), skip() and available(), and keep going past EOF.
• Treat anything other than IOException as a failure, including negative available()/skip() results.
• Enforce an allocation budget (e.g. ThreadMXBean.getThreadAllocatedBytes ≤ 32 MiB + 4096 × input length) to catch allocation amplification.

@FuzzTest public void frame_multi(FuzzedDataProvider d) { drive(d, false, false); }
// frame_single, block_stop, block_nostop ...

This will immediately flag the NPE on skippable-only streams, the RuntimeException on bad descriptors, and the per-frame buffer reallocation in LZ4FrameInputStream, so land those fixes first or together. Deep recursion on empty blocks needs more input than libFuzzer's default max_len, so cover it with a deterministic regression test instead.