Update sway-lib-core to meet SRC-2 inline docs standard (#4882)

## Description

This completes the never.sw, ops.sw, primitives.sw, and
primitive_conversions.sw tasks of
#4812

## Checklist

- [x] I have linked to any relevant issues.
- [x] I have commented my code, particularly in hard-to-understand
areas.
- [x] I have updated the documentation where relevant (API docs, the
reference, and the Sway book).
- [x] I have added tests that prove my fix is effective or that my
feature works.
- [x] I have added (or requested a maintainer to add) the necessary
`Breaking*` or `New Feature` labels where relevant.
- [x] I have done my best to ensure that my PR adheres to [the Fuel Labs
Code Review
Standards](https://github.com/FuelLabs/rfcs/blob/master/text/code-standards/external-contributors.md).
- [x] I have requested a review from the relevant team or maintainers.

---------

Co-authored-by: bitzoic <bitzoic.eth@gmail.com>

sway-lib-core/src/never.sw

@@ -4,10 +4,12 @@ use ::ops::{Eq, Not, Ord};
 
 /// `Never` represents the type of computations which never resolve to any value at all.
 ///
+/// # Additional Information
+///
 /// `break`, `continue` and `return` expressions also have type `Never`. For example we are allowed to
 /// write:
 ///
-/// ```
+/// ```sway
 /// let x: Never = {
 ///     return 123
 /// };
@@ -20,7 +22,7 @@ use ::ops::{Eq, Not, Ord};
 ///
 /// A more realistic usage of `Never` is in this code:
 ///
-/// ```
+/// ```sway
 /// let num: u32 = match get_a_number() {
 ///     Some(num) => num,
 ///     None => break,
@@ -33,13 +35,24 @@ use ::ops::{Eq, Not, Ord};
 ///
 /// Note that `Never` type coerces into any other type, another example of this would be:
 ///
-/// ```
+/// ```sway
 /// let x: u32 = {
 ///     return 123
 /// };
 /// ```
 ///
 /// Regardless of the type of `x`, the return block of type `Never` will always coerce into `x` type.
+/// 
+/// # Examples
+///
+/// ```sway
+/// fn foo() {
+///     let num: u64 = match Option::None::<u64> {
+///         Some(num) => num,
+///         None => return,
+///     };
+/// }
+/// ```
 pub enum Never {}
 
 impl Not for Never {