Use is-terminal instead of atty.

Following up on #3696, use the new is-terminal crate to test for a tty
rather than having platform-specific logic in Wasmtime. The is-terminal
crate has a platform-independent API which takes a handle.

This also updates the tree to cap-std 0.24 etc., to avoid depending on
multiple versions of io-lifetimes at once, as enforced by the cargo deny
check.

crates/test-programs/Cargo.toml

@@ -21,7 +21,7 @@ tempfile = "3.1.0"
 os_pipe = "0.9"
 anyhow = "1.0.19"
 wat = "1.0.37"
-cap-std = "0.22.0"
+cap-std = "0.24.0"
 tokio = { version = "1.8.0", features = ["rt-multi-thread"] }
 
 [features]