[feature]: `AddInvoice`: add ability to use only the best X quotes

[ZZiigguurraatt]

Currently when creating an asset invoice, if peer_pubkey is not defined, all peers are selected that have an asset channel of the specified asset_id. We should be able to choose to only use the best X quotes returned. If we have 10 channels, we may only want to use the best 4 quotes in the asset invoice.

This issue has a similar motivation as #1559 . Please take a look at #1559 for the motivation. This issue/feature could be used in combination with #1559 if implemented, but it is a separate (but simpler) issue/feature that targets the same problem in a slightly different but complimentary way.

[ZZiigguurraatt]

With #1613 incoming, we also need this for SendPayment.