Quick sketch adding derived cmd line arg parsing to veilid-cli

Quick sketch showing cmd line args via clap-derive (same underlying
parser, but simplifies cmd line parsing logic and reduces surface area
for potential bugs)

veilid-cli/Cargo.toml

@@ -27,7 +27,7 @@ cursive_buffered_backend = { path = "../external/cursive_buffered_backend" }
 cursive_table_view = "0.14.0"
 arboard = "3.2.0"
 # cursive-tabs = "0.5.0"
-clap = "^3"
+clap = {version= "4", features = ["derive"]}
 directories = "^4"
 log = "^0"
 futures = "^0"