help operators refactor (#13307)

# Description
Refactors `help operators` so that its output is always up to date with
the parser.

# User-Facing Changes
- The order of output rows for `help operators` was changed.
- `not` is now listed as a boolean operator instead of a comparison
operator.
- Edited some of the descriptions for the operators.

crates/nu-parser/src/parser.rs

@@ -4950,7 +4950,7 @@ pub fn parse_math_expression(
     let mut expr_stack: Vec<Expression> = vec![];
 
     let mut idx = 0;
-    let mut last_prec = 1000000;
+    let mut last_prec = u8::MAX;
 
     let first_span = working_set.get_span_contents(spans[0]);