fix: Make get_thousands_separator_uncached truly bypass locale cache

The test helper function get_thousands_separator_uncached() was calling
get_numeric_locale() which uses OnceLock for permanent caching. This
caused tests to fail intermittently on Ubuntu when test execution order
varied, as the first test would cache its locale value and subsequent
tests would receive that cached value instead of reading fresh env vars.

Changes:
- Made get_locale_from_env() pub(crate) in i18n/mod.rs
- Updated get_thousands_separator_uncached() to call get_locale_from_env()
  directly instead of the cached get_numeric_locale()

This ensures tests can properly change LC_NUMERIC environment variables
and see the effects immediately without cache interference.

Fixes Ubuntu test failures in:
- test_get_thousands_separator (line 423)
- test_format_with_thousands_separator_locale (line 383)

Author: naoNao89

src/uucore/src/lib/features/format/human.rs

@@ -149,8 +149,9 @@ fn get_thousands_separator() -> char {
 fn get_thousands_separator_uncached() -> char {
     #[cfg(feature = "i18n-decimal")]
     {
-        use crate::i18n::get_numeric_locale;
-        let (locale, _encoding) = get_numeric_locale();
+        use crate::i18n::get_locale_from_env;
+        // Bypass the cache by calling get_locale_from_env directly
+        let (locale, _encoding) = get_locale_from_env("LC_NUMERIC");
 
         // C and POSIX locales have no thousands separator
         // The default locale from i18n is en-US-posix for C/POSIX

src/uucore/src/lib/features/i18n/mod.rs

@@ -29,7 +29,7 @@ const DEFAULT_LOCALE: Locale = locale!("en-US-posix");
 /// 3. LANG
 ///
 /// Or fallback on Posix locale, with ASCII encoding.
-fn get_locale_from_env(locale_name: &str) -> (Locale, UEncoding) {
+pub(crate) fn get_locale_from_env(locale_name: &str) -> (Locale, UEncoding) {
     let locale_var = ["LC_ALL", locale_name, "LANG"]
         .iter()
         .find_map(|&key| std::env::var(key).ok());