fix: incorrect locale caching in message formatter

[michelheusschen]

The getMessageFormatter function calls monadicMemoize with a function that takes 2 parameters: message and locale. However, monadicMemoize only uses the first parameter for the cache key. This causes an issue when getMessageFormatter is called with the same message but a different locale:

// Correctly outputs 10,000
getMessageFormatter('{count, number} pages', 'en').format({ count: 10_000 })

// Incorrectly outputs 10,000 (expected 10.000)
getMessageFormatter('{count, number} pages', 'nl').format({ count: 10_000 })

Changes:

• Modify getMessageFormatter to call monadicMemoize with only one parameter
• Change the type of monadicMemoize to only accept one parameter to prevent recurrence
• Add unit tests to verify this scenario works correctly