feat(pcap): add operating system kernel name and release

Display the uname sysname and release as the OS option in the pcap Section
Header Block, falling back on just the std::env::consts::OS name ("linux") in
the case of runtime errors.

Co-authored-by: Nat Budin <natbudin@gmail.com>

lib/Cargo.toml

@@ -17,6 +17,7 @@ deku = { version = "0.16.0", features = ["logging"] }
 env_logger = "0.10.1"
 libc = "0.2.150"
 log = "0.4.20"
+nix = { version = "0.29.0", features = ["feature"] }
 pcap-file-tokio = "0.1.0"
 thiserror = "1.0.50"
 telcom-parser = { path = "../telcom-parser" }