feat(decompile): default openai_api_key to configured value if empty

[Jon-Becker]

Motivation

Solution

[github-actions]

Benchmark for 3d78676

Click to view benchmark

Test	Base	PR	%
heimdall_cfg/complex	13.4±0.64ms	14.3±0.89ms	+6.72%
heimdall_cfg/simple	1964.1±16.02µs	1990.0±42.86µs	+1.32%
heimdall_decoder/seaport	35.2±3.97µs	34.4±1.00µs	-2.27%
heimdall_decoder/transfer	3.7±0.33µs	3.4±0.29µs	-8.11%
heimdall_decoder/uniswap	11.1±1.01µs	10.4±0.46µs	-6.31%
heimdall_decompiler/abi_complex	55.0±5.34ms	52.9±4.93ms	-3.82%
heimdall_decompiler/abi_simple	2.1±0.09ms	2.1±0.01ms	0.00%
heimdall_decompiler/sol_complex	70.0±3.21ms	61.8±0.51ms	-11.71%
heimdall_decompiler/sol_simple	2.6±0.07ms	2.6±0.03ms	0.00%
heimdall_decompiler/yul_complex	61.3±5.52ms	55.8±3.03ms	-8.97%
heimdall_decompiler/yul_simple	2.3±0.07ms	2.3±0.02ms	0.00%
heimdall_disassembler/complex	781.1±106.51µs	714.1±27.71µs	-8.58%
heimdall_disassembler/simple	40.1±3.46µs	39.1±2.64µs	-2.49%
heimdall_vm/erc20_transfer	304.6±16.65µs	294.3±14.14µs	-3.38%
heimdall_vm/fib	715.2±26.26µs	705.0±22.37µs	-1.43%
heimdall_vm/ten_thousand_hashes	589.3±22.59ms	560.8±40.49ms	-4.84%