Use the newly extracted pipecheck crate

I decided to split this out from the rest of xt since I want to use it
in other projects, and it's _just_ complex enough that I don't want to
copy-paste it everywhere. (Really, the implementation isn't complex,
it's more that the documentation and reasoning behind it are complex.)

Author: featherbread

Cargo.lock

@@ -15,6 +15,7 @@ exclude = ["benches/**"]
 [dependencies]
 lexopt = "0.3.1"
 memmap2 = "0.9.4"
+pipecheck = "0.1.0"
 rmp = "0.8.12"
 rmp-serde = "1.1.2"
 serde = "1.0.196"

Cargo.toml

@@ -38,7 +38,6 @@ use xt::Format;
 
 #[macro_use]
 mod bail;
-mod pipecheck;
 
 fn main() {
 	let args = match Cli::parse_args() {