Use php-intl to format currencies

Currently the php function `number_format` is used to format currencies.
This is problematic as we have to figure out different things for
different currencies ourselves. These formats are determined based on
the libc's locale functions.

The issue arises where an OS doesn't have the proper locales installed,
or, in some cases, it's not supported (see below on multiple issues).

This addresses this issue by using the php-intl extensions to format the
numbers based on the locale. The extension is already a requirement in
`composer.json`. The solution does not rely on `LC_MONETARY` from the
underlying libc (which in Alpine Linux's case, which uses musl, is not
supported as of yet).

List of issues that are related and would potentially be fixed using
this PR:

- #2298
- #2946
- #3070
- #3306
- #3519

app/Support/Facades/Amount.php

@@ -38,7 +38,6 @@ use Illuminate\Support\Facades\Facade;
  * @method string getCurrencySymbol()
  * @method TransactionCurrency getDefaultCurrency()
  * @method TransactionCurrency getDefaultCurrencyByUser(User $user)
- * @method array getJsConfig(array $config)
  */
 class Amount extends Facade
 {