Support integer keys in query parameters

[Tigrov]

According to interface method description, there are no integer keys:

@param array $params The list of query parameter values indexed by parameter placeholders.
     * For example, `[':name' => 'Dan', ':age' => 31]`.

If it's true, we should throw exception on int keys.
If it's false, we should update interface phpdoc.

Would it be a mixed array with both int and string keys?

Originally posted by @vjik in #1116 (comment)

[Tigrov]

Would it be a mixed array with both int and string keys?

The answer is contained in the documentation https://www.php.net/manual/en/pdo.prepare.php

Both named and question mark parameter markers cannot be used within the same statement template; only one or the other parameter style.

[vjik]

So, we should update phpdoc.