Fuzz

Experimenting reducing stack size of `Error` #351

Job	Run time
fuzz (roundtrip_semantic)	3m 12s
fuzz (parse_descriptor)	3m 57s
fuzz (parse_descriptor_secret)	3m 12s
fuzz (roundtrip_miniscript_script)	3m 34s
fuzz (roundtrip_miniscript_str)	3m 21s
fuzz (roundtrip_descriptor)	3m 33s
fuzz (roundtrip_concrete)	3m 49s
fuzz (compile_descriptor)	3m 15s
verify-execution	7s
	28m 0s

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