(GH-1761) Fix locale-dependent prefetch failure in mysql_database provider - #1769

Summary

Fixes #1761.

mysql_database's self.instances rescues a missing database during prefetch by checking whether the mysql/mariadb client's error message contains the English string "Unknown database". When the server/client reports errors in another locale (the reporter saw this on RHEL 9 with MariaDB 11.4 under a German locale, which prints "Unbekannte Datenbank"), that string match fails, the exception is re-raised, and prefetch fails for every mysql_database resource in the catalog — not just the missing one.

This is especially easy to hit via mysql::server::account_security, which declares:

mysql_database { 'test':
  ensure  => 'absent',
  require => Anchor['mysql::server::end'],
}

The first run removes the test database as desired. Every run after that fails during prefetch, because the database is now legitimately absent and the client raises ERROR 1049 (42000): Unbekannte Datenbank 'test' (or the equivalent in whatever locale the DB is configured for), which the old check didn't recognize.

Fix

Match on the numeric MySQL/MariaDB error code 1049 (ER_BAD_DB_ERROR) instead of the localized message text, since the code is stable across locales while the message text is not.

Test plan

• Added a unit test reproducing the German-locale error string from the issue (ERROR 1049 (42000): Unbekannte Datenbank 'managed_missing') and confirming it's now handled the same as the English-locale case.
• Existing spec/unit/puppet/provider/mysql_database/mysql_spec.rb suite passes (17 examples, 0 failures).