Fulltext search breaks in mongodb when filters are enabled.

[funduck]

• With mongodb driver
• if query contains $fulltext
• and EntityManager applies filters

then error is thrown.

Stack trace

Error: Full text search is only supported on the top level of the query object.',
        '    at MongoDriver.renameFields (/app/node_modules/@mikro-orm/mongodb/MongoDriver.js:118:19)',
        '    at MongoDriver.find (/app/node_modules/@mikro-orm/mongodb/MongoDriver.js:23:22)',
        '    at MongoEntityManager.find (/app/node_modules/@mikro-orm/core/EntityManager.js:112:41)',
        '    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)',

To Reproduce
A simple test case

const god = new Author('God', 'hello@heaven.god');
const bible = new Book('Bible', god);
await orm.em.persistAndFlush(bible);
orm.em.clear();

const booksRepository = orm.em.getRepository(Book);
orm.em.addFilter('BreakFulltext', {title: {$re: '.*'}}, Book, true)
const books = await booksRepository.find({ $fulltext: 'Bible' })

Expected behavior
It should be possible to use full text search and use filters with Mongo driver.
Working example with Postgre:

const god = new Author2('God', 'hello@heaven.god');
const bible = new Book2('Bible', god);
await orm.em.persistAndFlush(bible);
orm.em.clear();

const booksRepository = orm.em.getRepository(Book2);
orm.em.addFilter('BreakFulltext', {title: {$re: '.*'}}, Book2, true);
const books = await booksRepository.find({ title: {$fulltext: 'Bible'} });

I propose following:

• if query has $and in top level and $fulltext in any of its elements, move it to top level
• if there are several $fulltext in $and or top level already has one throw an error