I18n: Prevent Intl.DateTimeFormat crash with invalid locales (#110522)

* fix: prevent Intl.DateTimeFormat crash with invalid locales like 'c'

- Add locale validation utilities to prevent crashes when LANG=c is set
- Filter out invalid locales from navigator.languages before creating DateTimeFormat
- Add fallback handling to use browser defaults when all locales are invalid
- Fixes issue #110494 where Grafana crashes with 'RangeError: Incorrect locale information provided'
- Maintains backward compatibility for valid locales

Signed-off-by: Akhil Singh <singhakhil69@gmail.com>

* refactor: simplify locale fix to use direct try-catch approach

- Remove locale-utils.ts and locale-utils.test.ts files
- Use simple try-catch in dates.ts files: try locale, fallback to 'en-US'
- Use Laura's suggested approach in formats.ts with explicit variable declaration
- Remove unused utility exports from index.ts
- Maintains same functionality with cleaner, simpler code
- Avoids adding to public API while still preventing crashes with invalid locales like 'c'

Signed-off-by: Akhil Singh <singhakhil69@gmail.com>

* style: run prettier to fix linting issues

- Format code according to project prettier configuration
- Fixes failing Lint Frontend check

Signed-off-by: Akhil Singh <singhakhil69@gmail.com>

---------

Signed-off-by: Akhil Singh <singhakhil69@gmail.com>

packages/grafana-data/src/datetime/formats.ts

@@ -105,7 +105,13 @@ export function localTimeFormat(
   }
 
   // https://momentjs.com/docs/#/displaying/format/
-  const dateTimeFormat = new Intl.DateTimeFormat(locale || undefined, options);
+  let dateTimeFormat: Intl.DateTimeFormat;
+
+  try {
+    dateTimeFormat = new Intl.DateTimeFormat(locale || undefined, options);
+  } catch {
+    dateTimeFormat = new Intl.DateTimeFormat('en-US', options);
+  }
   const parts = dateTimeFormat.formatToParts(new Date());
   const hour12 = dateTimeFormat.resolvedOptions().hour12;