feat(tvix/eval): Support builtins.tail

TL;DR:
- support `builtins.tail`
- define `ErrorKind::TailEmptyList` and canonical error code
- support basic unit tests

Unsure whether or not the error should be a dedicated `ErrorKind`...

Change-Id: Iae90fda1bb21ce7bdb1aaa2aeb2b8c1e6dcb0f05
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6545
Reviewed-by: wpcarro <wpcarro@gmail.com>
Autosubmit: wpcarro <wpcarro@gmail.com>
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

tvix/eval/src/errors.rs

@@ -31,6 +31,9 @@ pub enum ErrorKind {
         index: i64,
     },
 
+    /// Attempted to call `builtins.tail` on an empty list.
+    TailEmptyList,
+
     TypeError {
         expected: &'static str,
         actual: &'static str,
@@ -150,6 +153,8 @@ impl Error {
                 format!("list index '{}' is out of bounds", index)
             }
 
+            ErrorKind::TailEmptyList => format!("'tail' called on an empty list"),
+
             ErrorKind::TypeError { expected, actual } => format!(
                 "expected value of type '{}', but found a '{}'",
                 expected, actual
@@ -257,6 +262,7 @@ to a missing value in the attribute set(s) included via `with`."#,
             ErrorKind::NotAnAbsolutePath(_) => "E020",
             ErrorKind::ParseIntError(_) => "E021",
             ErrorKind::NegativeLength { .. } => "E022",
+            ErrorKind::TailEmptyList { .. } => "E023",
             ErrorKind::NotImplemented(_) => "E999",
         }
     }