Remove python-like string multiplication (#10293)

# Description
Currently we support "multiplication" of strings, resulting in a terse
way to repeat a particular string.
This can have unintended side effects when dealing with mixed data (e.g.
after parsing data that is not all numbers).
Furthermore as we frequently fall-back to strings while parsing source
code, this introduced a runaway edge case in const evaluation (#10212)

Work for #10233

## Details
- Remove python-like string multiplication.
- Workaround for indentation
  - This should probably be addressed with a purpose built command
- Remove special const-eval error test

# User-Facing Changes
**Major breaking change!**
`"string" * 42` will stop working. (This was used for example in the
stdlib)

We should bless a good alternative before landing this

---------

Co-authored-by: JT <547158+jntrnr@users.noreply.github.com>

crates/nu-command/tests/commands/math/mod.rs

@@ -498,11 +498,3 @@ fn append_binary_values() {
     ));
     assert_eq!(actual.out, "0x[01020304]");
 }
-
-#[test]
-fn int_multiple_string() {
-    let actual = nu!(pipeline(r#"3 * "ab""#));
-    assert_eq!(actual.out, "ababab");
-    let actual = nu!(pipeline(r#""ab" * 3"#));
-    assert_eq!(actual.out, "ababab");
-}