Make wallet constructor compatible with multipath descriptors

[andreasgriffin]

Describe the enhancement
BDK seems to include multipath descriptors (rust-miniscript PR and bdk support ). However bdk-ffi seems to require 2 separate descriptors.

Please enable, either

• Wallet creation from 1 multipath descriptor
• or expose the method to split 1 multipath descriptor into External and Internal descriptor.

Use case
Sparrow wallet supports multipath descriptors. They are more compact, and conceptually easier: 1 wallet = 1 multipath descriptor

[thunderbiscuit]

This is being added in bitcoindevkit/bdk_wallet#275.

[notmandatory]

bitcoindevkit/bdk_wallet#275 is merged and will be in the 2.1 release.

[reez]

bitcoindevkit/bdk_wallet#275 is merged and will be in the 2.1 release.

woo hoo!