rust/utils: Add Hexslice

Add a thin wrapper around [u8] to be able to represent an u8-slice as a
hex-string for Display and Serialize.

Acked-by: Qi Feng Huo <huoqif@cn.ibm.com>
Reviewed-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>

rust/utils/Cargo.toml

@@ -9,3 +9,4 @@ clap = { version ="4.1", features = ["derive", "wrap_help"] }
 libc = "0.2.49"
 log = { version = "0.4.6", features = ["std", "release_max_level_debug"] }
 pv = { path = "../pv" }
+serde = { version = "1.0.139"}