Make `pxe.getNotes(...)` include note nonces

[benesjan]

Currently we don't return note nonces from getNotes(...) and this forced us to expose getNoteNonces(...) on PXE when implementing the crowdfunding contract. We needed the nonce there because we used note inclusion proof to claim a reward token and note inclusion proof requires it.

I originally implemented the ExtendedNote type which is returned from getNotes and I didn't include there the nonce because it is also used when adding a note and we didn't need the nonce there at that time.

Note: Look for TODO(#4956) in the codebase.