Feature: Build chantools genimportscript natively into LND

[niteshbalusu11]

Background

As of today if a node goes down and the user does not possess an SCB, the only way to recover funds is to contact all peers and request force closures and then run chantools genimport script to recover funds stuck in lnd derivation branch since the funds do not automatically return to onchain wallet.
It would be nice if the genimportscript is built natively into lnd for the funds to automatically return to onchain wallet if peers initiate force closures.

[guggero]

Duplicate of #4778.

Once the above issue is fixed, the use of chantools genimportscript is no longer necessary.