Document public types in nu-protocol (#12906)

- **Doc-comment public `nu-protocol` modules**
- **Doccomment argument/signature/call stuff**
- **Doccomment cell path types**
- **Doccomment expression stuff**
- **Doccomment import patterns**
- **Doccomment pattern matching AST nodes**

crates/nu-protocol/src/value/record.rs

@@ -1,3 +1,4 @@
+//! Our insertion ordered map-type [`Record`]
 use std::{iter::FusedIterator, ops::RangeBounds};
 
 use crate::{ShellError, Span, Value};