Replaces the legacy pure-Python lookup table CRC32 implementation with the built-in `zlib.crc32`.
The previous implementation relied on a manual loop over bytes, which was inefficient for large firmware files (taking ~0.5s for 2MB on modern CPUs). The new implementation reduces this to ~1ms.
Implementation details:
- Removed the hardcoded `crctab` array to clean up the code.
- Adjusted `zlib` initial state (0xFFFFFFFF) and final XOR operations to ensure bit-perfect compatibility with the specific CRC32 variant expected by the PX4 bootloader.
Benchmark (2MB firmware):
- Legacy: ~0.48s
- zlib: ~0.001s
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