[feature]: `QueryRoutes` and `SendPaymentV2` should support multiple `last_hop_pubkey`

[feelancer21]

Is your feature request related to a problem? Please describe.
It is one building block to make pathfinding more efficient, especially for rebalancers.

Describe the solution you'd like
QueryRoutesRequest should support multiple last_hop_pubkey. To be consistent SendPaymentRequest should support it too. The associated lncli commands should also be adapted.

Describe alternatives you've considered
None