common: extract more code into separate crate

This extracts the remaining code from `src/common.rs` which does not
depend on other parts of the main library crate. No functional changes.

Closes #12310

src/tinyexpr.rs

@@ -34,6 +34,7 @@
     prelude::*,
     wutil::{Error as wcstodError, wcstod::wcstod_underscores},
 };
+use fish_common::assert_sorted_by_name;
 
 #[derive(Clone, Copy)]
 enum Function {