Move job errors into ShellError::Job variant (#15820)

- related #10698

# Description


In my endeavor to make the `ShellError` less crowded I moved the job
related errors into `ShellError::Job` with a `JobError` enum. Mostly I
just moved the codes, errors and labels over to the new enum.

crates/nu-engine/src/command_prelude.rs

@@ -6,5 +6,5 @@ pub use nu_protocol::{
     ast::CellPath,
     engine::{Call, Command, EngineState, Stack, StateWorkingSet},
     record,
-    shell_error::io::*,
+    shell_error::{io::*, job::*},
 };