Add missing `ZBytes::str` (#534) #3154

Job	Run time
Check zenoh-python using Rust 1.75	28s
check	1m 50s
markdown_lint	4s
build (3.11)	2m 48s
build (3.10)	2m 51s
build (3.9)	2m 57s
build (3.13-dev)	2m 58s
build (3.12)	2m 56s
CI status checks	2s
	16m 54s

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