Add support for fuzz testing using libFuzzer

[onethumb]

The Problem

We'd like to increase our confidence in the memory safety of this crate.

The Solution

Add extensive fuzz testing using libFuzzer.

Changes

• Adds fuzz tests for all the major CRC variants which use different hardware-accelerated paths (32, 64, reflected, forward, fusion, etc) for both checksum and Digest calculations.
• Update README.

Planned version bump

• Which: PATCH
• Why: non-breaking fuzz testing

[Copilot]

Pull Request Overview

This PR adds comprehensive fuzz testing infrastructure using libFuzzer to improve confidence in the memory safety of the crate's hardware-accelerated CRC implementations.

• Introduces 12 individual fuzz targets covering checksum and Digest calculations for all major CRC variants (32/64-bit, reflected/forward, fusion techniques)
• Adds fuzz testing configuration with dedicated Cargo workspace
• Documents memory safety validation approach in README

Reviewed Changes

Copilot reviewed 16 out of 17 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
fuzz/Cargo.toml	Configures fuzz testing workspace with libfuzzer-sys dependency and 12 bin targets for individual fuzz tests
fuzz/Cargo.lock	Lock file for fuzz testing dependencies
fuzz/.gitignore	Ignores fuzz testing artifacts (target, corpus, artifacts, coverage)
fuzz/fuzz_targets/digest_crc32_autosar.rs	Fuzz target for CRC-32/AUTOSAR Digest (reflected variant)
fuzz/fuzz_targets/digest_crc32_bzip2.rs	Fuzz target for CRC-32/BZIP2 Digest (forward variant)
fuzz/fuzz_targets/digest_crc32_iscsi.rs	Fuzz target for CRC-32/ISCSI Digest (reflected with x86/aarch64 fusion)
fuzz/fuzz_targets/digest_crc32_iso_hdlc.rs	Fuzz target for CRC-32/ISO-HDLC Digest (reflected with aarch64 fusion)
fuzz/fuzz_targets/digest_crc64_ecma_182.rs	Fuzz target for CRC-64/ECMA-182 Digest (forward variant)
fuzz/fuzz_targets/digest_crc64_nvme.rs	Fuzz target for CRC-64/NVME Digest (reflected variant)
fuzz/fuzz_targets/checksum_crc32_autosar.rs	Fuzz target for CRC-32/AUTOSAR checksum (reflected variant)
fuzz/fuzz_targets/checksum_crc32_bzip2.rs	Fuzz target for CRC-32/BZIP2 checksum (forward variant)
fuzz/fuzz_targets/checksum_crc32_iscsi.rs	Fuzz target for CRC-32/ISCSI checksum (reflected with x86/aarch64 fusion)
fuzz/fuzz_targets/checksum_crc32_iso_hdlc.rs	Fuzz target for CRC-32/ISO-HDLC checksum (reflected with aarch64 fusion)
fuzz/fuzz_targets/checksum_crc64_ecma_182.rs	Fuzz target for CRC-64/ECMA-182 checksum (forward variant)
fuzz/fuzz_targets/checksum_crc64_nvme.rs	Fuzz target for CRC-64/NVME checksum (reflected variant)
fuzz/fuzz_targets/digest.rs	General fuzz target file that is not configured in Cargo.toml and contains unused/incorrect code
README.md	Adds "Memory Safety" section documenting validation using Miri and libFuzzer

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