[feature]: Add LookUpAsset RPC

[GeorgeTsagk]

Description

If we want to retrieve asset information via our RPC we are currently limited to using ListAssets RPC. Even though this currently works alright it could be inefficient when the number of owned assets grows larger.

This could be somewhat improved with filters as described in #876, but maybe an explicit RPC call for this is also useful.

We should add a call that takes a specific asset_id (or a group key) and returns all assets currently owned by the wallet. Could also use similar params to ListAssets like include_spent/include_leased.