Minimize future false positive typos (#12751)

# Description

Make typos config more strict: ignore false positives where they occur.

1. Ignore only files with typos
2. Add regexp-s with context
3. Ignore variable names only in Rust code
4. Ignore only 1 "identifier"
5. Check dot files

🎁 Extra bonus: fix typos!!

tests/shell/pipeline/commands/external.rs

@@ -286,7 +286,7 @@ mod stdin_evaluation {
     fn does_not_panic_with_no_newline_in_stream() {
         let actual = nu!(pipeline(
             r#"
-                nu --testbin nonu "wheres the nuline?" | length
+                nu --testbin nonu "where's the nuline?" | length
             "#
         ));