When a model contains COMPRESSION_METADATA but the interpreter was built
without compression support, throw a RuntimeError with a helpful message
directing users to build with --//:with_compression=true.
The implementation uses inline functions in compression_utils.h
that are optimized away when compression is disabled, ensuring
all code paths remain compile-checked, and readable without
preprocessor clutter.
Includes test_compression_unsupported.py to verify the error detection,
which only runs when compression is disabled.
BUG=#3125
