Clarify that `<str>::from_utf8*` methods are aliases to `core::str::from_utf8*` functions

[sorairolake]

Location

• <str>::from_utf8
• <str>::from_utf8_mut
• <str>::from_utf8_unchecked
• <str>::from_utf8_unchecked_mut

Summary

These methods are aliases to core::str::from_utf8* functions.

So I think it would be better to mention this as follows:

/// This is an alias to [`core::str::from_utf8`].

This also makes it more clear that the results of <str>::from_utf8* methods and core::str::from_utf8* functions are the same.

[hanna-kruppe]

It’s probably better for the links to go in the other direction: the inherent functions are more idiomatic and easier to access, so they shouldn’t distract readers by pointing out the worse alternative. Actually deprecating the free functions is probably too much churn for the foreseeable future but now that the inherent methods are stable they can be recommended in the free functions’ docs.